First steps for importing managed objects
Merge branch 'develop' into feature/importing

Conflicts:
	CoreDataKit.xcodeproj/project.pbxproj
Make importing possible

not yet tested.
Make error types public

and document them
Document NamedManagedObject protocol
Fix renamed error code
Test create method
Share build scheme
Guard nil error pointers
Test find method
Document find method
Lot of little things for importing
Make saving more transparent and save

by creating an overload of performBlock that takes a block that tells us how the user wants to save it's data instead of always saving to persistent store with performBlockAndSaveToPersistentStore. Also created the helper method performBlockOnBackgroundContext to keep the most common use case short.
Merge branch 'feature/perform-changes-commit-action' into feature/importing
Merge branch 'feature/importing' into develop
Remove dangling debug code