Add `remove_map` server command

[Kaffeine]

There is a way to add a map to the rotation but no way to remove it.

teeworlds-infclassR/src/game/server/gamecontext.cpp

Line 4540 in 3848a03

Console()->Register("add_map", "?r[map]", CFGFLAG_SERVER, ConAddMap, this, "Add a map to the maps rotation list");