* refactor ms planner (renaming, reorganization)
* fix a bug originaly demonstrated by test_version_depends_on
* enhance crossed relation support, though there is still some bug renaming.
some tests were actually wrong.
Buggy tests (wether they fail or not, they are byggy) marked by XXXFIXME)
from warnings import warn
warn('moved to cubicweb.schema', DeprecationWarning, stacklevel=2)
from cubicweb.schema import *