Fixed the following warnings:
* Actor.add_actor deprecation warnings - replaced by Actor.add_child
* Actor.animate deprecation warnings - replaced by setting easing properties
* Actor.depth deprecation warnings - replaced with z-position
* Stage.color deprecation warning - replaced with Actor.background_color
* Group.new deprecation warning - replaced with Actor.new
* Clutter.Texture.from_file warning - replaced with Clutter.Image preloaded from a GdkPixbuf