[entity] Entity.related(): add a targettypes argument (closes #2957313)
This allows to restrict the entity types returned by the method
(passed to cw_related_rql).
When such an argument is given, no caching happens.
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')