Blackboard vs. Dynamic Entities

[ashoulson]

Dynamic Entities:

• Behave as they do now, producing and storing a state every tick and keeping a buffer of them

Blackboard Entities:

• Only produce a state when they change, meant for game state data or player data

Both should live in the state/entity stream and blackboards should occupy entity slots when filling packets.

[ashoulson]

Merge with #28, will be resolved when that's done. Slow-updating entities will work naturally in that system (just set them not to freeze).