chore(gui/resources): use restangular and centralized resource services

WIP :-)

With restangular and resource services, it's easier to handle/maintain REST API calls in AngularJS apps.

Planned TODOS:
- Move all rest API calls in services (no custom `$http` calls in Controllers)
- Use restangular for all REST based API calls

@bradrydzewski, what do you think about this?

Cheers :beer:
Sebastian