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
- added new functions:
* content::keyword::get_children
* content::keyword::get_keyword_id
* content::keyword::get_options_flat
* content::keyword::item_get_assigned
* content::keyword::item_unassign_children
- updated regression test
