Implemented retrieve core data methods in model objects.
Refactored enter data view controller.
Refactored activities view controller.
Added MessageUI framework.
Added set methods skeleton for model objects.
Implemented setter methods for model objects.
Implemented set label method for viewParticipationCell.
Added setup section headers method in view participations controller.
Refactored add/edit project view controller.
Merge branch 'refactoring'