Astrometry-azel

put radec and azel each in single plot

handle more corner cases

update test reference values from astropy

* LocateCrop.py finds where in a larger image a cropped image came from. This is a common case where a GUI is used to crop extraneous stuff from a larger image, particularly in amateur astronomy.
* azel + radec plots are now overlaid on the grayscale mean img used for all computations with non-square axes, a drastic improvement in plot quality
* _radec.png and _azel.png are now saved automatically.

This program currently assumes an observer very near Earth's surface. A warning is issued if any negative elevations are determined. This can be improved in the future if off-Earth observers are desired.

Don't overwrite input FITS, instead create a _stack.fits file with RA/DEC inside

fix -o output file writing.

* allow `.new` FITS files from astrometry.net web service to be used directly without renaming first
* streamline CI--probably will go to Azure Pipelines in future
* `black` style