Reintegrate real-time combat

[InspectorCaracal]

This uses an instanced combat handler and the cooldowns contrib to manage combat mechanics.

Adds:

• Melee and ranged combat instances
• Engage/flee, hit/shoot, advance/retreat commands
• Moving to a different room on successful flee
• Very basic death acknowledgement
• Preventing attacking players outside of PvP zones

Does NOT add:

• To-hit or damage mechanics
• Weapon prototypes
• Preventing exit traversal while in combat
• Actual death mechanics