[PythonCAD] Today's repo update

[Art Haas]

Hi.

There is lots of new things at the repo today. A good bit of work for
improving the Dimension undo/redo abilities, as well as a new menu
under 'Modify' -> 'Change' allowing various Dimension parameters to
be altered. Finally the UI provides a way to change things like
dimension color, endpoint type, endpoint size, etc. There are still
many more dimension parameters that need interface support for
adjustment, and hopefully I'll be able to add a few more goodies like
this before too long.

Art
-- 
Man once surrendering his reason, has no remaining guard against absurdities
the most monstrous, and like a ship without rudder, is the sport of every wind.

-Thomas Jefferson to James Smith, 1822