First pass at multi-string

@mogox @drtoast this works but the fades and refresh are quite slow.  I have a couple ideas about how to fix that - maybe even doing something like round robin updating each strip.  If we did that with 4 strips and each strip at 10ms to redraw that's a full redraw every 40ms which is 25fps - not too shabby.  I guess the first step would be seeing how long it's actually taking to repaint all the LEDs.