Lobby to optionally require TLS certificate and certificate verification, refs #4737, #5257.

These are config options because developers should be able to test a local lobby server quickly without going through the hassle to create a valid or invalid certificate or modify and compile the client.
To protect from malicious JS mods reducing these security config options, these options as well as the hostname would have to be protected from JS access.
The user might still connect to other lobbies through a hypothetical UI if there were a non-modifiable GUI confirmation dialog prior to the connection.

Proofreading and feature design discussion by Vladislav and Dunedan on irc on 2018-08-19 and 2018-08-23.