Add new solarized light and dark themes.

Add more elements to be controlled by theme css:
- Preloader spinner colours
- Operation disable / breakpoint icons
- Auto bake checkbox
- Search highlight colour
- Categories header colour

src/web/stylesheets/themes/_classic.css

@@ -36,6 +36,13 @@
     --banner-font-colour: #468847;
     --banner-bg-colour: #dff0d8;
 
+    --category-list-font-colour: #1976d2;
+
+    --loader-background-colour: var(--secondary-border-colour);
+    --loader-outer-colour: #3498db;
+    --loader-middle-colour: #e74c3c;
+    --loader-inner-colour: #f9c922;
+
 
     /* Operation colours */
     --op-list-operation-font-colour: #3a87ad;
@@ -76,6 +83,13 @@
     --arg-label-colour: #388e3c;
 
 
+    /* Operation buttons */
+    --disable-icon-colour: #9e9e9e;
+    --disable-icon-selected-colour: #f44336;
+    --breakpoint-icon-colour: #9e9e9e;
+    --breakpoint-icon-selected-colour: #f44336;
+
+
     /* Buttons */
     --btn-default-font-colour: #333;
     --btn-default-bg-colour: #fff;
@@ -114,4 +128,5 @@
     --popover-border-colour: #ccc;
     --code-background: #f9f2f4;
     --code-font-colour: #c7254e;
+    --input-highlight-colour: #1976d2;
 }