Porting more server functionality

In this check-in, I've included the bulk of the rest of the logic that
was previously running on the client, including:

- Fixes for enemy spawning
- Attack, loot generation, and leveling code
- A* pathfinding which has been integrated into enemy AI
- Network messaging for enemy movement
- Enemy AI
- Cleanup of code into multiple DLLs
- Addition of namespaces to codebase

Holy shit. More to come.