[BL_GenericAPIResponse]: Add a new class to map a generic response from the server
[AppCakeAPI]: Finalise the user registration method and add a new method to handle log ins
[AC_User]: Modify the AC_User class according to the remote data model
[BLImportItem]: Add the copyright notice in the file header
[Barrel Project]: Add the new classes to the project
[OEHUDAlert]: Handle the alertWithError method and make it display the NSError's error description
[XIBs]: Make the Preferences XIBs compatible with Xcode 5 DP4
[BLPrefUserController]: Add actions to the register and login buttons