Remove unused code

There will be more trimming later, but this is a good start:
trimming code that's completely unused now.
Put format-conversion functions in separate module
Move visualization functions to separate module

The pairwise function is duplicated here, but that will change in
the next commit when I'll move it (and some other useful utility
functions) to its own module.
Move even more functions into own module
Moved general-purpose functions to own module

General-purpose functions are ones that generally don't rely on too
many other pieces of code to work -- like averagepoint() or pairwise().
They are the lowest-level units of functionality.
Remove a bit more unused code and comments
Remove time.sleep() call between line segments

While I'm working on refactoring, I don't want the time.sleep()
call slowing me down as I repeatedly run the code.
Add standard .gitignore file for Python

This is the default .gitignore file created by Github when you ask
for a new repository and say you'll be doing Python development. It
contains sensible .gitignore wildcards that nearly every Python-based
project will want to use.
Move a few more functions into general library
Draw each "world" separately

Each isolated polygon, plus its holes, can be drawn in a separate
"world". This commit makes it so, then superimposes the resulting
midline sets to get a total picture.