Optimize notefield drawing

[Kangaroux]

• [x] Draw the beat line paths in bulk (one beginPath and closePath call for all measure lines, beat lines, fractional lines)
• [ ] Resize the noteskin images when the skin or note size changes [1]

[1] https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Optimizing_canvas#don%E2%80%99t_scale_images_in_drawimage