[2.0.0] Remove isis_formatter and usgscsm_formatter

[jrcain-usgs]

Fixes #653

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]

Everything looks good but a breaking change like this would require a version tick to ALE 2.0.0. In ISIS we usually hold any breaking change for the yearly release, I don't know what we should do for ALE. With the spiceql changes and the gdal additions we could likely do a 2.0.0. @Kelvinrr thoughts?

[Kelvinrr]

we should probably hold off on this for this reason. At least we should see if there are more API breaking changes we can pile on.

[oleg-alexandrov]

The code removed is ancient and not used by anybody. Likely ALE 2.0.0 bump is needed simply because of adding the ShadowCam lens distortion which breaks the enums.

I'd say the risk of this is very low. Also, likely next ISIS need to have a hard pin to this as well, and with usgscsm and spiceql too, all because of ShadowCam. There's no good reason for the user to want independent versions for these.

[oleg-alexandrov]

This should be merged, presumably because so many things broke as is in ALE, with inclusion of shadowcam lens distortion model, that this minor breaking change that removes dead code is small by comparison.

[oleg-alexandrov]

This PR must be merged and the dead code has to go. This situation has been around for 3-4 years by now, and any time one studies the ALE code one is misled by three ways of doing things, out of which only one has ever worked since that time. By now it is inevitable there will be a USGSCSM 2.0 or some major bump in light of the newly added CaSSIS and KPLO ShadowCam lens distortion models. Having this drag on is just burden on developers with no upside.

[oleg-alexandrov]

For the record, the current approach of making an ISD has been the default since 2020-03-31, shipped in 0.8.0 on
2020-04-12. Nobody uses the other approaches even if they make use of ALE, unless they explcitily ask for the old format and not contented with the default, which I don't see any reason for.