More fixes and changes

Few map fixes and changes
Extra protection against voiding
Tiny fix to undropable items
Imperio will not work anymore if your target is also using Imperio
Fixes #19 - Vaults will unload after 5 seconds of last person exiting them 
Fixes #22 - You can no longer gain points in house wars during round setup
Fixes #24 -  Evanesco will no longer work against flying players 
Fixes #36 -  Text output of spells/items can now be seen by invisible people 
Fixes #30 -  Freeze Area now unfreezes if already GM frozen 
Fixes #38 -  Deatheater PMing someone who has full inbox will no longer reveal them