render smoothly while drawing

cache points as we record them without drawing,
then compute the beziers and stroke.

this leaves a lag between the rendered curve and the actual
mouse position
move bezierCurve into settings
choose whether to render linear or bezier for sig collection
temporarily draw the linear bits for responsiveness
comment: todo item for shorter bezier paths
Redraw canvas on mouseup for beziers
Remove hard coded pen color used during debugging