make pixel-make-pixel more general, use it to create indentation too
rename tools -> toolbar
rename pixel-make-face -> pixel-make-hover-face, add pixel-copy-hover-face
first try to implement canvas resize, commiting before throwing it away
huge code rework, useable version

- basic drawing should work now without problems
- starting implementing a method to show changes while dragging the
  mouse, before releasing the mouse button so you can see what you are
  drawing
- code cleanup and reordering of stuff