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.
More work getting MacOS build process to work.
Avoid excessive number of floating point digits of
output in the demo tests, so that insignificant
floating point variations don't cause unit test failures.
The demo tests on Mac OS failed because of very tiny
floating point discrepancies that don't matter.
Changed the output of the "Moon check" so that slight
differences in vector residue no longer fail the unit tests.
