Move rst files to generated folder hierarchy

[texasaggie97-zz]

[X] This contribution adheres to [CONTRIBUTING.md]

What does this Pull Request accomplish?

• Moves generated rst files into generated/docs
  • All files generated as part of the build now in generated
  • References in toctree cannot reference out of own hierarchy, so reference *._link.rst that use rst .. include:: directive to pull in the generated files

Why should this Pull Request be merged?

• Keeps generated files in single location

What testing has been done?

• Travis & ReadTheDocs

[coveralls]

Coverage remained the same at 60.54% when pulling b9a62ed on build/move_rst_to_generated into 65f37e1 on master.

[marcoskirsch]

After discussing with @texasaggie97 , we aren't convinced that overall, this is better than just living with generated files in docs.

We're going to close, may revisit at some point in the future.