Massive refactor

- Use contextual namespaces within Flarum\Core
- Clean up and docblock everything
- Refactor Activity/Notification blueprint stuff
- Refactor Formatter stuff
- Refactor Search stuff
- Upgrade to JSON-API 1.0
- Removed “addedPosts” and “removedPosts” relationships from discussion
API. This was used for adding/removing event posts after renaming a
discussion etc. Instead we should make an additional request to get all
new posts

Todo:
- Fix Extenders and extensions
- Get rid of repository interfaces
- Fix other bugs I’ve inevitably introduced

js/forum/src/components/composer.js

@@ -208,6 +208,7 @@ class Composer extends Component {
     if (flexible.length) {
       flexible.height(height -
         (flexible.offset().top - this.$().offset().top) -
+        parseInt(flexible.css('padding-bottom')) -
         this.$('.text-editor-controls').outerHeight(true));
     }
   }