Library: SynthDesc makeGui: Prevent non-ControlSpecs from making sliders
Library: SynthDesc gui: Synchronize Start button with synth's state
Library: SynthDesc gui: Less wasteful layout for arrayed controls
Library: SynthDesc gui: Fix epic uninitted-variable bug; remove debug post

The uninitialized variable meant that the slider values would be
ignored when clicking Start.
Library: SynthDesc GUI: Fix stuck notes b/c of unnecessary 's.bind'