inherit document level options and allow mapped-superclass to have all options

fix http://www.doctrine-project.org/jira/browse/PHPCR-77

there is two kind-of BC breaks:

* we now throw exception when explicitly setting referenceable to false after it was true in parent class
* we inherit document level options, which we did not before, so if people where relying on this wrong behaviour they can't anymore

i chose to allow all options on mapped-superclass as well, makes no sense to not allow some.