smooth drawing using bezier curves

+ BezierCurveConvertor
  to convert array of [x, y] to array of [x, y] with coordinats of bezier curves
+ Pass new options to Sketcher for smoother drawing
  . stroke_linecap
  . stroke_linejoin
m Different order of adding paths in Sketcher
  usual path is displayed while dragging, bezier curve is displayed on finish

[Delivers #52173503]