Added hasAttribute method to cryson entity.
nil check prevents unexpected TypeErrors
Added findOrRefreshByClass:andIds:fetch:delegate to CrysonSession.
Avoid KVO on entity refresh for unchanged attributes
Trigger dirty callbacks and handle dirty checking for persisted and deleted entities consistently with behaviour for updated entities.
Fix for broken @OneToOne associations. Use @OneToOne in examples again. Updated jersey. Bumped version to 0.5.16.