break up mapper->class relationship to be based on entity names
right now mappers are associated to classes via the class object itself. add a layer of indirection here, use "entity name", which defaults to the name of the class (possibly with package info added in). support making completely different mappers for the same class that are both "primary mappers". add an "_entity_name" attribute to classes and object instances to keep it straight.
this is totally from hiberate. id imagine as i read more and more hibernate docs, expect to see many more of these tickets :)
making this critical since its an architectural change....want to get as many of these out the door ASAP.