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    problems such as silent failures in `npm outdated` and `npm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/bin/deb-src/sysroot/etc/init/etherpad.conf

@@ -0,0 +1,28 @@
+description "etherpad"
+
+start on started networking
+stop on runlevel [!2345]
+
+env EPHOME=/opt/etherpad
+env EPLOGS=/var/log/etherpad
+env EPUSER=etherpad
+
+respawn
+
+pre-start script
+    cd $EPHOME
+    mkdir $EPLOGS                        ||true
+    chown $EPUSER $EPLOGS                ||true
+    chmod 0755 $EPLOGS                   ||true
+    chown -R $EPUSER $EPHOME/var         ||true
+    $EPHOME/bin/installDeps.sh >> $EPLOGS/error.log || { stop; exit 1; }
+end script
+
+script
+  cd $EPHOME/
+  exec su -s /bin/sh -c 'exec "$0" "$@"' $EPUSER -- node node_modules/ep_etherpad-lite/node/server.js \
+                        >> $EPLOGS/access.log \
+                        2>> $EPLOGS/error.log
+  echo "Etherpad is running on http://localhost:9001 - To change settings edit /opt/etherpad/settings.json"
+
+end script