mash-light-box: Override the ClutterContainer add and remove methods
mash-light-box: Override the ClutterContainer add and remove methods

This overrides the add and remove methods of ClutterContainer so that
it could detect when the number of MashLights changes and regenerate
the shader.

clutter-project/mash,eliasbakken/mash,clutter-project/mash,eliasbakken/mash,clutter-project/mash