Fixed tiny typo in description of /lac
buggy god-mode implementation using creative mode
God mode working fully, refactored some stuff

Removed redundant calls (mostly removePotionEffect), implemented
debilitatePlayer and rehabPlayer. The former locks down the player (eg.
not logged in), and the latter restores the player (teleport, unblind,
un-godMode).
Removed redundant damage-related event handlers
removed one more redundant event handler
pass name to rehabPlayer and debilitatePlayer
made player even more blind with night vision

night vision + blindness = pitch black screen
admin command no longer needs lower case username
fixed blindness (misplaced braces)
Stored player's old gamemode as metadata

Also refactored the code used to prompt the player for an action upon
joining into a method called playerJoinPrompt
fixee: call debilitatePlayer from playerJoinPrompt

so that session resuming works as intended
fix: call debilitatePlayer from playerJoinPrompt
Fixed: do not teleport players on /logout, otherwise location is lost
fix: creative mode exploit using /logout
preparations for re-writing godmode
Revert "removed one more redundant event handler"

This reverts commit ce89b5c94853d810b57e35714efb141cbfef4858.
Revert "Removed redundant damage-related event handlers"

This reverts commit ec83ef3ba095183083435dc1628507c50a01a4ca.
re-implemented god mode by adding more listeners, and minor formatting
mobs no longer target unauthenticated players
added anti-drowning, removed night vision potion effect

Otherwise, a legitimate night vision potion effect might be removed by
the plugin