NbtkTable: move nbtk_table_add_actor logic into nbtk_container_add_actor
NbtkTable: move nbtk_table_add_actor logic into nbtk_container_add_actor

Ensures that clutter_container_add works as expected

jonnylamb/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx