Removed 0.17 requirement note from formula docs

0.17 is no longer a supported release.
Moved the Formula Conventions CHANGELOG section down next to Versioning

This section is less important for new users than the mapfile and sls
recommendation sections.
Improve and shorten the Formula lookup table recommendation
Updated the Formula README recommendation
Added link targets to a few requisite types
Improved the simple Formula usage example at the top
Improved the Formula installation docs with examples
Improve and clarify the Formula docs on using formulas from non-formulas
Moved the Formula repository structure docs to the bottom

We should describe best practices for writing formulas first.
Fleshed out the recommendations for writing reusable formulas
Removed the redundant platform agnostic Formula section
Fleshed out Formula Parameterization section
Merge pull request #14790 from whiteinge/doc-formulas-update

Misc cleanups, clarifications, and additions to the formulas conventions doc