add threshold on selections, add 'deselect' when just clicking canvas beyond this threshold
fix for selection of signal without moving (moving was causing redraw, we need to redraw everytime)
added basic draw canvas -> change zoom functionality
only draws wave expression when there are multiple waves
fix .draw() of addbutton onclick while hovering, change drawCurve to take start point -> simulate dephasage (imperfectly)
add play button (not nice implementation; not scalable)
fix bug where dragging wasn't reset when squashing a signal, refactored a lot; generalized buttons, split out some methods of graphesizer for clarity
add playback functionality - lacking sound and a (good) way to interact with waves while playing