Add World Stats

[ted537]

closes #434

https://user-images.githubusercontent.com/8276517/132250730-fee1f2ee-0a54-40ad-b487-a4913c03f5fc.mp4

Note that since crafting/ammo systems are not present, the "item created" and "item consumed" events have not been connected to any player action yet.

Changes

• track agent type IDs
• log event upon agent death
• add command for printing world stats
• add world stats
• remove outdated references to WorldState