Add UserGroup to chill (import from branch ticket-app-master)

Import the UserGrou feature from ticket-app-master branch. This includes:

- import all the entities and migrations, modification of typescript types, templating, and so on;
- apply some verification and formatting rules, like:
  - reformat file on chill.api.specs.yaml (MainBundle)
  - reformat file on types.ts (Main Bundle)

Migrations kept the same filename.

src/Bundle/ChillMainBundle/Resources/views/Entity/user_group.html.twig

@@ -0,0 +1 @@
+<span class="badge-user-group" style="color: {{ user_group.foregroundColor }}; background-color: {{  user_group.backgroundColor }};">{{ user_group.label|localize_translatable_string }}</span>