remove whitespaces and some old debug code
fix regex not capturing types correctly
comment out some unused stuff
fix bug that palette from other buffer could not be used

- also use markers instead of points to avoid confusion
add some mode specific stuff to pixel-regex

- in particular try to read width/height in lisp like modes
don't disable and enable undo when entering pixel-mode
simplify make-hover-face so it's faster

- also create one keymap and reuse that instead of creating one for
  every pixel
get rid of background and foreground in bitmap
canvas replace and resize stuff