Adds Sensor Util Functions

[amystamile-usgs]

Licensing

This project is mostly composed of free and unencumbered software released into the public domain, and we are unlikely to accept contributions that are not also released into the public domain. Somewhere near the top of each file should have these words:

This work is free and unencumbered software released into the public domain. In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain.

• I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

[acpaquette]

Overall a good translation of the functions from the SensorUtils library into knoten. A lot of my concerns are how coupled we want to make this with CSM and the amount of work that may be necessary to replicate some of the functionality in ISIS. Mainly getting Illumination "stuff" into knoten for use.

The other issue is shapemodels. If PSMRTS is ready for use relatively soon I see this as a none issue. If that's not the case or we decide not to adopt it, we will have to home roll a fair amount of shapemodel stuff.

There is some deviation from the function signatures w.r.t. shapemodel. I think providing a shape argument and a very barebones ellipsoid model would be enough

[amystamile-usgs]

@acpaquette I believe I made all the changes you suggested. Let me know if I went the right direction with this. If so, I will work on fixing the tests and docs.

[acpaquette]

Looks fantastic! One small thing to address but feel free to update tests