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

framework/core/js/src/common/Translator.js

@@ -1,6 +1,5 @@
 import User from './models/User';
 import username from './helpers/username';
-import extractText from './utils/extractText';
 import extract from './utils/extract';
 
 /**
@@ -23,6 +22,10 @@ export default class Translator {
     this.locale = null;
   }
 
+  addTranslations(translations) {
+    Object.assign(this.translations, translations);
+  }
+
   trans(id, parameters) {
     const translation = this.translations[id];