Refactors most controllers and directives into classes for more organized and maintainable code

app/assets/javascripts/services/singletonManager.js

@@ -0,0 +1,10 @@
+import { SFSingletonManager } from 'snjs';
+
+export class SingletonManager extends SFSingletonManager {
+  // constructor needed for angularjs injection to work
+  // eslint-disable-next-line no-useless-constructor
+  /* @ngInject */
+  constructor(modelManager, syncManager) {
+    super(modelManager, syncManager);
+  }
+}