[DO NOT MERGE UNTIL XMAS] Dev freeze 0.19 staging

Fun changes!

Antags now have no objectives and are allowed to have all the funs! 8813123
NanoUI for APCs + All kinds of new backend changes for NanoUI (87c246f /  214fbee / c9191fa)
Engine room redesign (#4318)
New Posters and removal of TG posters (#4277)
Mixing paint (#4276)
Supermatter updates (#4303)
Multi-Z level support (#4309)
Dionaea updates and IPC (new species) creation (#4352)
New...newer shuttle (#4367)
New Airlock controller and UI (#4408)
and much more!