Various updates to nasa_exoplanet_archive core.py: Add and clean up units in UNIT_MAPPER. Comment out warning about new default table when using query_object(). Fix units and remove masking in _fix_units() to avoid errors and warnings from astropy (since QTable coenversion can't handle any columns with units that also have masked values).
Various updates to nasa_exoplanet_archive core.py: Add and clean up units in UNIT_MAPPER. Comment out warning about new default table when using query_object(). Fix units and remove masking in _fix_units() to avoid errors and warnings from astropy (since QTable coenversion can't handle any columns with units that also have masked values).

ceb8/astroquery,imbasimba/astroquery,imbasimba/astroquery,ceb8/astroquery