* Lots and lots of CSS finetuning. I believe I can't make it any better

  than this, only CSS gurus should be able to improve it even more.

* On the coding side, file edit widgets are now real form elements.
  That means no buttons for such widgets, but instead they can come up
  with their own value callbacks and widget theme functions.
  Plus I now have them in their walled garden where they belong.