Create NSPersistentStoreCoordinator factory method that can accept a model as an argument.
Add helper to create an in memory persistent store coordinator with a specific managed object model.
Added unit tests for NSPersistentStoreCoordinator factory functions.
Expose MR_obtainPermanentIDsBeforeSaving
Merge pull request #1 from sewichi/sewichi_develop

Rebasing commits on top of updated develop branch.