Following #5913, mod_ipstamp is no longer required to enable STUN
hosting (it can only be useful to enable non-STUN hosting).
This updates the readme to reflect that, and fixes some markdown issues.
Differential Revision: https://code.wildfiregames.com/D3473
This was SVN commit r24857.
Yields a more transparent directory structure, in particular when adding
the third bot or systemd service files.
Refs: #3022, D1659, D1661.
Comments by: user1, Dunedan
This was SVN commit r21926.