Another huge commit, sigh, see below

I really should start trying to split these up, but when it's a solo
project...

 - Added simplify.js to clientside
 - Split up BrushManager.drawPath() into initPaths() and redraw()
 - Changed LocalBrush to go through the BrushManager, instead of using
   its own Brush (side effect is that BrushManager can save the paths)
 - Now fully supports resizing by simplifying and saving paths in
   BrushManager