[storages] fix fs_importing side-effect on entity.data
When creating a new File object, if fs_importing is set,
we want entity.data to be the file content instead of the
filepath for the rest of the transaction.
(see test_bfss_fs_importing_transparency) for test implementation
To make this possible, the storage hooks (entity_added / entity_updated)
must return the correct value to set in the entity dict.
# Instructions here will be read before reading the schema
"""
:organization: Logilab
:copyright: 2001-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""
# You could create your own groups here, like in :
# create_entity('CWGroup', name=u'mygroup')