Rgb image

This adds loading of images (png, jpeg,...) to RGB matrices.

Images can be static, scrolled horizontally or vertically, and played as an animation.
There is a sample workspace in etc/RGBImage/

I had to add pointer to Doc to all RGBScripts, so that I can convert paths when loading/saving workspace.

TODO: QLC+ crashes when the image path edit box is manually changed. Loading image through dialog works fine.

I also created static function for 1000 (index of volume bar) in vcaudiotriggers.