v6.0.0

Major overhaul of the server! This release introduces custom games 😄

This means that a server can now stay online and host multiple tournaments at once. To achieve this it introduces the concept of a "Lobby", which is a namespace within the socket channel that players can join.

A lobby is managed from the web GUI, where any user can create a new lobby, share the URL with other players, connect uabc algorithms to it, and trigger the start of a new tournament.

From this release on, the major versions of uabc and ultimate-ttt-web will be coordinated, and will only be compatible if they match.