add MAST query tool for coronagraphy datasets

[mperrin]

This PR adds a function spaceKLIP.mast.query_coron_datasets for searching MAST for available coronagraphic science, PSF reference, and/or background data. This PR includes the code and an example notebook.

Example usage is like:

# Find all available NIRCam PSF references in a given filter for the 335R mask
query_coron_datasets('NIRCam', 'F335M', 'MASKA335R', kind='REF')

# Find all MIRI 15 micron background observations
query_coron_datasets('MIRI', 'F1550C', kind='BKG')

The returned output is an astropy table like:

[additional rows not shown]

[kammerje]

Thanks a lot @mperrin, this is very helpful!