Efl.Ui.Bg_Widget: added Efl.Ui.Bg_Widget.Part_bg part to support "background" part name
update the code
API parts (any part referenced in library code) must be namespaced. All of the SWALLOW parts in the efl/bg group should be in the format 'efl.NAME'
currently, this patch is not available. I will abandon this :)
Based on @herb 's comment, this patch is abandoned.