[selector] allow inplace operator in selector computation Intended to facilitate overriding of existing selectors chain in view declaration. It make the code shorter and clearer when you've to import long module pathnames

# pylint: disable-msg=W0614,W0401
from warnings import warn
warn('moved to cubicweb.dataimport', DeprecationWarning, stacklevel=2)
from cubicweb.dataimport import *