Removes a lot of duplicated code and rationalize the behaviour, as orm_memory should have the same features as regular orm (inheritance, properties etc. Note: removed *on purpose* the code from revision qdp-launchpad@tinyerp.com-20100628120010-kk2b7v94om0kpam1 that gave incorrect default values for orm_memory objects. It should not be needed anyway. bzr revid: odo@openerp.com-20100813150955-7a3vqj9iywb3706s