* move wiki pages to synapse/docs and add a few titles where necessary
* update SUMMARY.md with added pages
* add changelog
* move incorrectly located newsfragment
* update changelog number
* snake case added files and update summary.md accordingly
* update issue/pr links
* update relative links to docs
* update changelog to indicate that we moved wiki pages to the docs and state reasoning
* requested changes to admin_faq.md
* requested changes to database_maintenance_tools.md
* requested changes to understanding_synapse_through_graphana_graphs.md
* add changelog
* fix leftover merge errata
* fix unwanted changes from merge
* use two spaces between entries
* outdent code blocks
