Completely reworked site documentation - Done (for now)

Merge Notes:

All documents were proof read, their date modified updated, all the links in them changed to the new filename format, and all HTML output verified using pelican.

Document Titles are only temporary until categories and static position assignment for the documents is set up in pelican. E.g. The $ in $ Donate is only there to keep it at the top of the list and the ~ before the policies are to keep them at the bottom.

Unlike the Titles, document filenames intentionally feature the category short-form in front of them now (e.g. pol-code-of-conduct.md, feat-mechanics-design.md), and IMO should remain that way in order to help organize them in the /content/pages directory and make them easier to find when sorted alphabetically. Either that or each category should be given its own directory at some point (which is probably a better idea).

Document Summary: sections left blank since they make the docs sidebar unwieldy, IMO. I moved the document summaries to the page_index.html instead.

Let me know if there is anything that needs changing before merge request can be accepted.

p.s. If you accept, don't forget to update the links on the main site to reflect the new document filenames. E.g. The new_topic page references both the text-formatting and topic-tagging docs, which have now been changed to guide-text-formatting and guide-topic-tagging, respectively. The comment boxes on the site (reply and new top-level) also reference the the text-formatting doc.