Frontend refactor (#1471)

Refactor Frontend + Asset code

- Use Laravel's Filesystem component for asset IO, meaning theoretically
  assets should be storable on S3 etc.

- More reliable checking for asset recompilation when debug mode is on,
  so you don't have to constantly delete the compiled assets to force
  a recompile. Should also fix issues with locale JS files being
  recompiled with the same name and cached.

- Remove JavaScript minification, because it will be done by Webpack
  (exception is for the TextFormatter JS).

- Add support for JS sourcemaps.

- Separate frontend view and assets completely. This is an important
  distinction because frontend assets are compiled independent of a
  request, whereas putting together a view depends on a request.

- Bind frontend view/asset factory instances to the container (in
  service providers) rather than subclassing. Asset and content
  populators can be added to these factories – these are simply objects
  that populate the asset compilers or the view with information.

- Add RouteHandlerFactory functions that make it easy to hook up a
  frontend controller with a frontend instance ± some content.

- Remove the need for "nojs"

- Fix cache:clear command

- Recompile assets when settings/enabled extensions change

src/Api/Controller/SetSettingsController.php

@@ -11,8 +11,7 @@
 
 namespace Flarum\Api\Controller;
 
-use Flarum\Settings\Event\Saved;
-use Flarum\Settings\Event\Serializing;
+use Flarum\Settings\Event;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Flarum\User\AssertPermissionTrait;
 use Illuminate\Contracts\Events\Dispatcher;
@@ -53,14 +52,16 @@ class SetSettingsController implements RequestHandlerInterface
 
         $settings = $request->getParsedBody();
 
+        $this->dispatcher->dispatch(new Event\Saving($settings));
+
         foreach ($settings as $k => $v) {
-            $this->dispatcher->dispatch(new Serializing($k, $v));
+            $this->dispatcher->dispatch(new Event\Serializing($k, $v));
 
             $this->settings->set($k, $v);
-
-            $this->dispatcher->dispatch(new Saved($k, $v));
         }
 
+        $this->dispatcher->dispatch(new Event\Saved($settings));
+
         return new EmptyResponse(204);
     }
 }