null gamemode

[NotAFile]

@10se1ucgo mentioned in #26 the ability to set a game mode that just tells the client to turn off all of it's existing game mode logic. No scorekeeping, default entities, etc.

Of course, this requires replicating the existing gamemode features first to be useful, so it needs at least #3 to be useful for modes like arena and #11 to create more complex game modes.

[iamgreaser]

I'd advise tying this in with #3 , and allocating it as a game mode type which has notably less information in whatever the game init packet is called, possibly also having a way to disable scoring full-stop. I'll propose something in that issue, but a null mode which defaults to no team scores should be fine even on its own.

The usual fallback for vanilla will most likely be to pick CTF and shove the tents and intels into the top-left corner of the map.