Apply transforms cleanup changes

[ZackAttack614]

Overview

This PR removes a lot of unused and dead code from the transforms module of HEXRD. We aniticpate that this may affect users who have very old scripts (5 years or more) or others who have used the xf or old_xfcapi components of the library. As this code has not been supported in many years, it is time for this code to be removed from the library. We will support the transition to the newer code as needed, on a case-by-case basis.

Some documentation about transitioning from the old_xfcapi code can be found in the Wiki:

https://github.com/HEXRD/hexrd/wiki/old_xfcapi-Conversion-Guide

Affected Workflows

Users who have scripts which use the old_xfcapi or xf components of HEXRD's transforms module will need to move off of this and into the new API, using the conversion guide above.

Documentation Changes

Documentation regarding transition has been written, and uploaded into the Github Wiki. Documentation covering the removed code has been deleted.

[codecov]

Codecov Report

❌ Patch coverage is 82.11921% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.69%. Comparing base (f6268a2) to head (2d1a285).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
hexrd/core/transforms/xfcapi.py	81.87%	27 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #891      +/-   ##
==========================================
+ Coverage   69.41%   70.69%   +1.27%     
==========================================
  Files         148      142       -6     
  Lines       22590    22058     -532     
==========================================
- Hits        15680    15593      -87     
+ Misses       6910     6465     -445     

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[psavery]

I'm assuming most of this file was just copied over from old files like xf_new_capi.py. I did a brief skim over it but I'm assuming it's fine.

[psavery]

LGTM

The corresponding branch in the GUI (HEXRD/hexrdgui#1964) seems to be working well also.

We may have a discussion with users before merging, since this will break code.