Dimension dialog

Got dimension dialog working; this is the File...New menu item.
Miscellaneous edits to get kakuroCSP working.  Passes tests on small
puzzles, but way too slow on realistic ones.
Changed clue entry to scale widgets

This way, you don't have to use both keyboard and mouse.  This allowed
cleanup of a lot of code, since user can't entehr bad clues.  I also
disabled the scales in squares where clues can't be enetered.  I changed
the CSP solver to limit the domains of the variables to possibilities
depending on the clues, instead of always making them 1-9, but I haven't
done any testing.