I refactored the unit tests for all the demo programs
to follow a different pattern that makes it simpler
to add more demo tests in the future.
The main thing is that correct output and generated
output are now in separate directories `correct` and `test`.
I have moved the test scripts from `test/test` to `./demotest`
in all the langauge demo directories.
This makes it simpler to clean up any stale generated
files before each test run by `rm -f test/*.txt`.
I stumbled across this while making the Java demo tests,
and it was a better solution, so now all the other languages
are consistent with the Java demo tests.
In the C demo tests, I also decided to compile all the
binary executables into a subdirectory `bin` that can
be cleaned out before each run, to make sure there are
no stale executables from an earlier run.
I forgot that Mac OS does not have sha256sum
installed by default. This caused the worldmap
demo test to fail, trying to confirm that I got
the output PNG image I expected.
The demo worldmap.cpp now also prints out the
geographic locations where the Sun/Moon appear
to be straight up (at the zenith) for the given time.
This illustrates that Astronomy_VectorObserver can
turn a geocentric vector into a location on the
Earth that is in the same direction from the Earth's
center that a given celestial body lies.
The worldmap.cpp demo was calculating each pixel's
observer location twice. Now it does so only once.
Added verification that the output PNG file is
exactly as expected, using a sha256 checksum.
The new demo worldmap.cpp generates a PNG image of
a Mercator projection of the Earth, showing color-coded
intensity of sunlight (yellow) and moonlight (blue).
This sample program shows how to efficiently calculate
horizontal altitudes of the Sun and Moon across many
different geographic locations, for a given observation time.
