Fix modules for new backend

src/app/models/content-group.ts

+export class ContentGroup {
+  name: string;
+  contentIds: string[];
+  autoSort: boolean;
+
+  constructor(name: string, contentIds: string[], autoSort: boolean) {
+    this.name = name;
+    this.contentIds = contentIds;
+    this.autoSort = autoSort;
+  }
+}

src/app/models/room.ts

+import { ContentGroup } from './content-group';
+
 export class Room {
   id: string;
   revision: string;
@@ -6,5 +8,5 @@ export class Room {
   name: string;
   description: string;
   closed: boolean;
-  contentGroups: {[key: string]: [string]};
+  contentGroups: ContentGroup[];
 }