Skirmish Update

• Implemented engagement value calculations and broadcast, and nullification when unconscious.
• Added per-class engagement data.
• Implemented Engagement table, which tallies up incoming engagement values, and tracks which entity is on top of the list.
• Implemented Threat-by-damage tracking, with an appropriate table and top-tracking as well.
• Added a new type of AI state called a Behavior. The only existing one is called 'Attack by Aggro'. The main scenario has been rewritten to start this state on the hostile NPCs. As expected, this state starts idle, and invokes an Attack Target whenever the top entity in threat (taking the greater of damage and engagement threat) changes.
• Aggro works! The game is fundamentally different to play, and works masssively better.