Fixed synchronization issues with multiple instances of the same store on iOS (until now NSDistributedNotificationCenter was missing)
Fixed font trait addition on iOS

This issue was causing failures in attributed string tests.
Rewrote font trait addition to use the same code on both Mac OS X and iOS
Fixed NSColor vs UIColor metamodel issue in tests

Note: All tests pass now on both Mac OS X and iOS.
Reintroduced font trait addition code specific to Mac OS X, -fontWithDescriptor:size: is broken

Note: All tests now truly pass on both Mac OS X and iOS.