restructure: move bin/ and tests/ to src/

Also add symlinks from the old `bin/` and `tests/` locations to avoid
breaking scripts and other tools.

Motivations:

  * Scripts and tests no longer have to do dubious things like:

        require('ep_etherpad-lite/node_modules/foo')

    to access packages installed as dependencies in
    `src/package.json`.

  * Plugins can access the backend test helper library in a non-hacky
    way:

        require('ep_etherpad-lite/tests/backend/common')

  * We can delete the top-level `package.json` without breaking our
    ability to lint the files in `bin/` and `tests/`.

    Deleting the top-level `package.json` has downsides: It will cause
    `npm` to print warnings whenever plugins are installed, npm will
    no longer be able to enforce a plugin's peer dependency on
    ep_etherpad-lite, and npm will keep deleting the
    `node_modules/ep_etherpad-lite` symlink that points to `../src`.

    But there are significant upsides to deleting the top-level
    `package.json`: It will drastically speed up plugin installation
    because `npm` doesn't have to recursively walk the dependencies in
    `src/package.json`. Also, deleting the top-level `package.json`
    avoids npm's horrible dependency hoisting behavior (where it moves
    stuff from `src/node_modules/` to the top-level `node_modules/`
    directory). Dependency hoisting causes numerous mysterious
    problems such as silent failures in `npm outdated` and `npm
    update`. Dependency hoisting also breaks plugins that do:

        require('ep_etherpad-lite/node_modules/foo')

src/tests/frontend/runner.js

@@ -0,0 +1,184 @@
+'use strict';
+
+/* global specs_list */
+
+$(() => {
+  const stringifyException = (exception) => {
+    let err = exception.stack || exception.toString();
+
+    // FF / Opera do not add the message
+    if (!~err.indexOf(exception.message)) {
+      err = `${exception.message}\n${err}`;
+    }
+
+    // <=IE7 stringifies to [Object Error]. Since it can be overloaded, we
+    // check for the result of the stringifying.
+    if (err === '[object Error]') err = exception.message;
+
+    // Safari doesn't give you a stack. Let's at least provide a source line.
+    if (!exception.stack && exception.sourceURL && exception.line !== undefined) {
+      err += `\n(${exception.sourceURL}:${exception.line})`;
+    }
+
+    return err;
+  };
+
+  const customRunner = (runner) => {
+    const stats = {suites: 0, tests: 0, passes: 0, pending: 0, failures: 0};
+    let level = 0;
+
+    if (!runner) return;
+
+    runner.on('start', () => {
+      stats.start = new Date();
+    });
+
+    runner.on('suite', (suite) => {
+      suite.root || stats.suites++;
+      if (suite.root) return;
+      append(suite.title);
+      level++;
+    });
+
+    runner.on('suite end', (suite) => {
+      if (suite.root) return;
+      level--;
+
+      if (level === 0) {
+        append('');
+      }
+    });
+
+    // Scroll down test display after each test
+    const mochaEl = $('#mocha')[0];
+    runner.on('test', () => {
+      mochaEl.scrollTop = mochaEl.scrollHeight;
+    });
+
+    // max time a test is allowed to run
+    // TODO this should be lowered once timeslider_revision.js is faster
+    let killTimeout;
+    runner.on('test end', () => {
+      stats.tests++;
+    });
+
+    runner.on('pass', (test) => {
+      if (killTimeout) clearTimeout(killTimeout);
+      killTimeout = setTimeout(() => {
+        append('FINISHED - [red]no test started since 3 minutes, tests stopped[clear]');
+      }, 60000 * 3);
+
+      const medium = test.slow() / 2;
+      test.speed = test.duration > test.slow()
+        ? 'slow'
+        : test.duration > medium
+          ? 'medium'
+          : 'fast';
+
+      stats.passes++;
+      append(`-> [green]PASSED[clear] : ${test.title}   ${test.duration} ms`);
+    });
+
+    runner.on('fail', (test, err) => {
+      if (killTimeout) clearTimeout(killTimeout);
+      killTimeout = setTimeout(() => {
+        append('FINISHED - [red]no test started since 3 minutes, tests stopped[clear]');
+      }, 60000 * 3);
+
+      stats.failures++;
+      test.err = err;
+      append(`-> [red]FAILED[clear] : ${test.title} ${stringifyException(test.err)}`);
+    });
+
+    runner.on('pending', (test) => {
+      if (killTimeout) clearTimeout(killTimeout);
+      killTimeout = setTimeout(() => {
+        append('FINISHED - [red]no test started since 3 minutes, tests stopped[clear]');
+      }, 60000 * 3);
+
+      stats.pending++;
+      append(`-> [yellow]PENDING[clear]: ${test.title}`);
+    });
+
+    const $console = $('#console');
+    const append = (text) => {
+      const oldText = $console.text();
+
+      let space = '';
+      for (let i = 0; i < level * 2; i++) {
+        space += ' ';
+      }
+
+      let splitedText = '';
+      _(text.split('\n')).each((line) => {
+        while (line.length > 0) {
+          const split = line.substr(0, 100);
+          line = line.substr(100);
+          if (splitedText.length > 0) splitedText += '\n';
+          splitedText += split;
+        }
+      });
+
+      // indent all lines with the given amount of space
+      const newText = _(splitedText.split('\n')).map((line) => space + line).join('\\n');
+
+      $console.text(`${oldText + newText}\\n`);
+    };
+
+    const total = runner.total;
+    runner.on('end', () => {
+      stats.end = new Date();
+      stats.duration = stats.end - stats.start;
+      const minutes = Math.floor(stats.duration / 1000 / 60);
+      // chrome < 57 does not like this .toString().padStart('2', '0');
+      const seconds = Math.round((stats.duration / 1000) % 60);
+      if (stats.tests === total) {
+        append(`FINISHED - ${stats.passes} tests passed, ${stats.failures} tests failed, ` +
+               `${stats.pending} pending, duration: ${minutes}:${seconds}`);
+      } else if (stats.tests > total) {
+        append(`FINISHED - but more tests than planned returned ${stats.passes} tests passed, ` +
+               `${stats.failures} tests failed, ${stats.pending} pending, ` +
+               `duration: ${minutes}:${seconds}`);
+        append(`${total} tests, but ${stats.tests} returned. ` +
+               'There is probably a problem with your async code or error handling, ' +
+               'see https://github.com/mochajs/mocha/issues/1327');
+      } else {
+        append(`FINISHED - but not all tests returned ${stats.passes} tests passed, ` +
+               `${stats.failures} tests failed, ${stats.pending} tests pending, ` +
+               `duration: ${minutes}:${seconds}`);
+        append(`${total} tests, but only ${stats.tests} returned. ` +
+               'Check for failed before/beforeEach-hooks (no `test end` is called for them ' +
+               'and subsequent tests of the same suite are skipped), ' +
+               'see https://github.com/mochajs/mocha/pull/1043');
+      }
+    });
+  };
+
+  const getURLParameter = (name) => (new URLSearchParams(location.search)).get(name);
+
+  // get the list of specs and filter it if requested
+  const specs = specs_list.slice();
+
+  // inject spec scripts into the dom
+  const $body = $('body');
+  $.each(specs, (i, spec) => {
+    // if the spec isn't a plugin spec which means the spec file might be in a different subfolder
+    if (!spec.startsWith('/')) {
+      $body.append(`<script src="specs/${spec}"></script>`);
+    } else {
+      $body.append(`<script src="${spec}"></script>`);
+    }
+  });
+
+  // initialize the test helper
+  helper.init(() => {
+    // configure and start the test framework
+    const grep = getURLParameter('grep');
+    if (grep != null) {
+      mocha.grep(grep);
+    }
+
+    const runner = mocha.run();
+    customRunner(runner);
+  });
+});