Fixed opacity brush rendering:
- Element render transforms no longer affect opacity brushes
- Special opacity handling in brushes no longer required
- Effects and opacity brushes can now be used together
Merge branch 'master' of https://github.com/MediaPortal/MediaPortal-2

Conflicts:
	MediaPortal/Source/UI/SkinEngine/Controls/Brushes/VideoBrush.cs
	MediaPortal/Source/UI/SkinEngine/Controls/Brushes/VisualBrush.cs
	MediaPortal/Source/UI/SkinEngine/Controls/Visuals/BackgroundEffect.cs
	MediaPortal/Source/UI/SkinEngine/Controls/Visuals/FrameworkElement.cs
	MediaPortal/Source/UI/SkinEngine/Skin/default/shaders/lineargradient_opacity.fx
	MediaPortal/Source/UI/SkinEngine/Skin/default/shaders/radialgradient_opacity.fx