Add SourceTV relayserver support

[ulrichblock]

HL1 + HL2 based servers support stand alone TV server. Structure can be the same as with a normal gameserver.

• Add a switch "relayserver" at GS part (admin)
• At overview add sort function gs/relay (admin)
• Enhance gs api with same flag and default to NO
• Introduce new menu point relay server (user)
• User should be able to enter IP:PORT and optional relay server password
• Check needed how GameQ works with relay server

[ulrichblock]

Too long in the backlog and never request.