add 'jquery-ui-rails' gem
resize sketcher

+ add callbacks function for scaler
  . afterZoomIn
  . afterZoomOut
  . afterBackToOrigin

[Delivers #52172447]
refactor: drawing methods into Drawer class
fix: after click the last path disappears

Solutions was to check if path with bezier curves had any points.
Don't add path, if there is no points

[Delivers #52365153]