refactor(*): extract a service to get the user list. KAB-170

Before:
- Fetching the user list directly inside the controller

After:
- Fetching the user list using the User service
fix(Room controller): onlineContacts should under $scope.data .KAB-170
refactor(Room controller): rename the model

Before:
- onlineContacts

After
- users
Merge branch 'kab-170' into 0.4.0-alpha.2

Refactor: user contacts should be handle by the service