added information about the naming conventions in schema.py
also:
* some typo fix
* note about ObjectRelation soon being deprecated
* clarified a few hazy points
"""pre 3.6 bw compat"""# pylint: disable-msg=W0614,W0401fromwarningsimportwarnwarn('moved to cubicweb.mixins',DeprecationWarning,stacklevel=2)fromcubicweb.mixinsimport*