Fixed|libappfw: Failed assert when deiniting widget not part of tree

Widgets should remember which atlas they have been using and not
ask the root widget, which may not be available any more.
Renderer|FX: Moved color filter later in the FX stack

If color filter is applied before bloom, it can alter the resulting hue
and brightness of the filter quite much.

Also, as the color filter is used for pain/etc. effects (visualization
for things that the player senses) they should be applied after the
optical effects.