Updates to get kalisiris working and improved subpix (#578)

* Updates to get kalisiris working and improved subpix

* Updates ground for kali changes

* Moves DEM into an interface and adds the ability to use an ellipsoid (#576)

* Moved DEM to an interface

* Actually added surface

* Added new options to demo config

* Updated Surface doc strings

Co-authored-by: jlaura <jlaura@usgs.gov>

* image_to_ground fix (#580)

* test(test_isis.py): image_to_ground() failure with map-projected image and single lon and lat.

* test(test_isis.py): image_to_ground() failure with non-map-projected image and arrays of lon and lat.

* fix(spatial/isis.py): image_to_ground() now properly returns correct values or numpy arrays, tests improved.

* working ground control

* Collection of minor changes for the 0.6.0 release to ensure functioning code. Tested in quad generation.

* Updates for PR comments; removed duplicitive bytescale call

Co-authored-by: Jesse Mapel <jmapel@usgs.gov>
Co-authored-by: Ross Beyer <rbeyer@rossbeyer.net>