Memcached_DataObject now defines
* pkeyGetClass to avoid collision with Managed_DataObject pkeyGet
* getClassKV to avoid collision with Managed_DataObject getKV
The parent class for our database objects, Managed_DataObject, has a
dynamically assigned class in staticGet which objects get put into,
leaving us with less code to do the same thing.
We will probably have to move away from the DB_DataObject 'staticGet'
call as it is nowadays deprecated.