FIX: BaseRepository Create method now returns ClassModel type
Added check for null exception in Collection.Add method
Merge branch 'master' of https://github.com/ArtemZag/academy13

Conflicts:
	BinaryStudio.PhotoGallery.Models/UserModel.cs
Merge branch 'master' of https://github.com/ArtemZag/academy13

Conflicts:
	BinaryStudio.PhotoGallery.Models/UserModel.cs