cleanup in cr::keyword::* namespace one cannot advocate to create a keyword with content::keyword::item_assign and query it with cr::keyword::item_get_assigned)
- marked the following function as deprecaed * cr::keyword::get_children * cr::keyword::get_keyword_id * cr::keyword::get_options_flat * cr::keyword::item_get_assigned * cr::keyword::item_unassign * cr::keyword::item_unassign_children