widget: Apply color_class parent-child relationship

widget: Apply color_class parent-child relationship

It removes color_class hashes from elm_widget.
The color_class hash can be removed if we use the following function
to update color classes of internal objects: edje_object_color_class_parent_set().
But, the color_class hash of Elm_Widget_Item has to be maintained.
Because, the edje object of item could be recreated without recreation of Elm_Widget_Item.

@tizen_feature

Change-Id: I40cabe27a3d4976d47258479a2aac58a27ddac45