offline mode, initial checkin - added option to store game locally and play it without network connection  
new code:
  iPhoneClient/Offline/
  server/sync
changes to original code:
  - JSONConnection 
     #import "JSONConnection+Local.h"
     using performAsynchronousLocalRequestWithHandler: and performSynchronousRequestLocal
  - Game.h, added offlineMode
  - AppModel.m, changed the way to get managedObjectModel so that it does not interfere with offline managedObjectModel
  - GameDetailsViewController.m, added "Download Game" option for offline games
added overlays to offline cache
Merge remote-tracking branch 'origin/feature-offline' into develop

Conflicts:
	services/v1/overlays.php
Merge branch 'develop' of https://github.com/ARISGames/server into develop