Implement Mission handling

[arves100]

Mission Start logic currently doesn't exist.

Packets for missions should be documented and placed their definitions in the packet generator, then actual handling code should start by perhaps loading data out of JSON (I belive JSON would also be easier for people to create their own missions)

A reference implementation, in my opinion, would contain the implementation of the tutorial mission which would (in the future) allow us to implement the tutorial flag of the game.

[Seltraeh]

I'll be resuming IDA digging and starting MST definitions soon. I'm hoping to utilize the packet generator after I better understand what it is I'm looking at in missions. Unfortunately, the libgame.so has over 40 unique classes with there own subroutines all tied to missions and it's become a tracing nightmare. I would have better odds of slowly mapping all of the MST's and JSON structs than trying to discover a "place of origin" that makes missions appear on the mission select screen.