Use mypy to check all Python demo programs.
Updated the demos to pass type checking.
There were a couple of small mistakes found, so this was worth the effort.
The phrase "Moon phase" is ambiguous, because sometimes
it means relative ecliptic longitude, other times it means
illuminated fraction. The "moonphase" demos were only
calculating the relative ecliptic longitude, which was
confusing. Now they calculate both.
Created skeleton test harness for validating the demo programs.
Created stub moonphase.py.
Copied correct demo program outputs from nodejs; will tweak as needed.
Call the Python demo test harness from the 'run' script.
