Port documentation makefile to .py

[cspotcode]

This will need to be rebased after #1710, since it branches off of #1710. Or we can merge this, bring in both PRs at once.

[pushfoo]

This works as-is on my system (Linux).

I think someone other than the contributors should give feedback on the following:

1. Are the changes to the variable names at the top ok (s/PAPER/PAPER_SIZE/)?
2. Should we still provide a stub makefile for backward compatibility with programmer habits / brevity?

[Cleptomania]

I think providing a Makefile in addition to this is going to cause problems. It just adds something else to maintain and creates a divergence in how Arcade is developed. Having everyone using the same process is much simpler.

[cspotcode]

As I imagine it, the stub Makefile would be no more than:

.PHONY html
html:
    python ./make.py html
# repeat...

It would be emitted by make.py at startup, but also committed to git, so would be kept in sync automatically.