[fti] refactor and fix full text indexation handling * moved logic from repository to the native source * avoid creating a FTIndexOp when no full text indexation is needed * entities with fulltext_container set are not indexed even when not related to a container * avoid duplicated unindexation

"""pre 3.6 bw compat"""
# pylint: disable-msg=W0614,W0401
from warnings import warn
warn('moved to cubicweb.mixins', DeprecationWarning, stacklevel=2)
from cubicweb.mixins import *