* Make all links indirect for better maintenance
* Add Domain section with `coturn.example.com` and use it in subsequent
examples
* Add standard ports for TURN and TURNS
* Remove TURNS-over-UDP (unknown whether it is supported)
* Add section on opening ports with ufw commands
* IMPORTANT: Move password auth/guest access instructions into the
Appendix as they are very insecure
* Small improvements in Testing section
* Rewrite Troubleshooting section to be more concise and cut down on
errors
* Add note to Eturnal in Appendix section