Add support for more gamemodes

Multiple gamemodes for a level will need to use the same navmesh,

Gamemodes to implement:

• [x] Conquest/Conquest Assault
• [x] Rush
• [x] TDM
• [x] SQDM
• [x] CTF
• [x] GM

Behaviours to implement:

• [x] Get out of vehicle once at objective
• [x] Defend flag carrier (CTF)

TODO: abstract gamemode controller to simplify implementation into custom modes and BF4