These lines should pull gps variable name from config 'source' attribute rather than use hard-coded

[jessecusack]

This code is not robust to config variable name changes:

glide/src/glide/qc.py

Lines 312 to 313 in a4c6120

	gps_lon = ds.m_gps_lon.values
	gps_lat = ds.m_gps_lat.values

[jessecusack]

We might need to specify a mandatory set of variables to include that are required, regardless of what is included in the config.