Add smooth animations to toggle buttons

[unfa]

I think that a quick fade when enabling/disabling controls would add lots of perceived polish to the interface.

This could be a simple thing that'd make things look more alive and inspiring. Possibly disabable in the settings if the users don't want it.

[fundamental]

These sorts of things could be generalized from the triggerbutton widget which already uses animations to show when clicked.

Unfortunately the implementation of such animatios will be somewhat clunky since the design of animation meta-widgets was never translated over from Qt's QML approach.