efl_ui_widget: add new internal EAPI for new group name

efl_ui_widget: add new internal EAPI for new group name

theme_klass: set/get klass name used for resize_obj
theme_element: set/get group name used for resize_obj
theme_style: set/get style name used for resize_obj
element_update: automatically sets and apply theme for
             sub object of widget.