Userprofile editing updates

User profile can now be edited with:
- Skills
- Themes
- Countries
- Tags (not fully functional)

This update includes the overriden "hasMany" and "dirtyRecrodsForHasManyChange" functions to change many2many relations via Ember and the api. The current functions do not break the implementation of the tagging Mixin of the API. However, the tags in a user profile are not loaded properly via Ember. They are saved correctly to the API.

The update also changes the serializer for the ProjectTheme model. Instead of a "title" field the serializer now consistently uses the "name" field of the model.