Remove all remains of unused auto-mode

Gamemode changes are now restricted by admin status and practice mode.
Fix functionality for CoreGoal. Requires testing.

`/ar core <team>` should add a core for a team.
Clean up logic for lobby worlds. Closes #121
Remove unused code
Add command to set lobby world in-game
TNT propogation event listener is a MONITOR
Add recognition for TNT, Creepers, and other exploding things.
Fix entity damage prevention by spectators. Fixes #128