[PythonCAD] Repo updates with TextBlock undo/redo code

[Art Haas]

Hi.

The public repo has some more stuff in it now. There is a new
TextBlockLog class which handles the undo/redo code for TextBlock
instances, and the Layer code has be modified to behave better when
undoing a TextBlock addition. There was a bug report about this last
week, and the root of the problem was that the info the Layer stores
when adding a new entity was lacking for TextBlocks.  Now, a TextBlock
can be added, then the addition can be undone without generating an
error. You can even redo the addition, then undo it again, then redo it,
then undo it ad infinitum.

I'm still aiming to make the seventeenth release this month. The
sixteenth release came out in the middle of June, so another release is
due. The next release will have printing capabilities, as well as
improved text behavior, so this upcoming release will be a major
advancement in the program. The lack of printing has been a big problem,
and I am eager to release the program with this shortcoming now fixed.

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