Minor efficiency improvement
No longer sets allow_pvp:false for game world
Added short delay before setting gamemode on join so multiverse doesn't override it.
Bugfix: exit_item config didn't work if it was changed from the default iron_door
Small bugfix - players in spectator mode were missing the Exit item in their hotbar.
- Various improvements to code design & style in response to feedback on the Denizen Discord. - 1 minor bugfix (error logged on disconnect from server) - No changes to the game functionality
