prepare for Starling integration, simplify Blendmode settings
Add support for Starling. Rework rendering to make it more simple and flexible. Rename "spin" to "rotate" and "angular velocity" to "rotation speed".

Missing features/bugs:
Starling sims cannot use sprite sheets.
Change alpha action on Starling sims does not work correctly in some cases.
Changing renderer causes most of the rendering settings to be lost.
Backgrounds obstruct simulations if using Starling renderer