NSFetchedResultsController category added

Signed-off-by: Felix Gabel <felix.gabel@me.com>
minor fixes

Signed-off-by: Felix Gabel <felix.gabel@me.com>
small changes
-all_load flag added to Test Target
forgot to remove -childContextWithConcurrencyType method implementation
2 NSFetchRequest convenience methods added
adding more convenient methods to NSFetchedResultsController