Strategy notes:

• This will make the documentation-theme-utils module obsolete. The utils it provided were initially intended for HTML themes, but were useful enough that documentation itself had a dependency, and we don't have a sufficient level of pluggability for it to make sense as a module.
• It also refactors interlinking to make it more flexible and more stable
  • We'll have a linker module that resolves links in a robust way that works with lots of templates
  • And be able to handle custom type links, like if you want Point to go to GeoJSON documentation etc
  • And linking will be more uniform between Markdown and HTML output
• Functional linker
• Documentation for helper methods