[PythonCAD] First take at command interpreter now available

[Art Haas]

Hi.

Thanks to the work of David Broadwell, PythonCAD now has its first
implementation of a command interpreter. The commands are stored in the
file 'keywords.py'; I'll add some documentation on the website giving the
available commands shortly.

A simple example to try is type 'hcl', and you'll be set to draw
horizontal construction lines. After adding a few, hit the Escape key so
that you'll see the 'Enter Command' prompt above the entry box at the
bottom of the screen. Hitting Escape should now stop whatever you are
doing and returning you to the point where you can select a drawing
operation of some type.

The code is up on the mirror, so give it a run. Now that the first
version of the interpreter has been added, I'll be making a release most
likely this weekend. I have a few more tweaks I want to add.

Art
-- 
To announce that there must be no criticism of the President, or that we
are to stand by the President, right or wrong, is not only unpatriotic
and servile, but is morally treasonable to the American public.
 -- Theodore Roosevelt, Kansas City Star, 1918