Multiplayer Functionality

Restore the multiplayer functionality we had before and add the necessary menu functionality

IN-GAME STUFF

[ ] opacity of other players becomes more transparent the closer they are to the main player's character
[ ] in-game server leaderboard when holding TAB
[ ] map runtime/cycling (a timer for how much longer the server is running the map should show on screen and the server should switch to the next map when the time is up)
[ ] in-game chat
[ ] winner podium shot when map time ends(top three players posing next to their unicycles), give a brief countdown for the next map to start to let players trash talk/congratulate/gg a little

MAIN MENU STUFF

[ ] Main Menu - quick play(automatically joins an official facepunch server with people in it if possible)
[ ] Main Menu - server list
[ ] Main Menu - create room

see here for more details on main menu functionality

Facepunch / sbox-unicycle-frenzy