All Example view controllers now inherit from ABExampleViewController

Sets backgroundColor to white to avoid visual artefacts under iOS  when
pushing to navigation stack
Bumped Example projects deployment target to iOS 7
ABNetworkingExample: Use new API
ABSaveSystemExample: Use new API
Compile without warning with iOS 7.1 SDK
ABNetworking: Simplified API
UIScreen Category: Added statusBarHeight method
ABStroeKitHelper: Use new ABSaveSystem API
ABView: "animateBackgroundColor" property is now "animateBackground" and applies to both backgroundColor and backgroundImage
ABSaveSystem:

- More sane method naming
- Truncation now deletes files instead of accidentally creating new ones
- Fixed bug causing “encrypted” attribute being overridden by
“ABSAVESYSTEM_ENCRYPTION_ENABLED” definition in saveData:key:encryped:
method