Some minor cleaning in ETController, ETNibOwner and persistency related categories
Removed dead code in ETNibOwner and removed COREOBJECT macro uses
Moved some persistency tests to TestFreeLayoutPersistency
Moved shape and basic item style persistency tests to TestStylePersistency
Rewrote and renamed TestPersistency to TestItemPersistency

Added support for calling -checkWithExistingAndNewRootObject:inBlock: multiple times in the same test method.
Fixed local variable hiding ivar warnings