The variables possible are:
* %player% - the player's last known name
* %uuid% - the player's uuid, or what can fit on a sign
* %reason% - the reason the player was jailed
* %jailer% - the person/thing who jailed this player
* %afktime% - the amount of time the player has been afk
* %timeinminutes% - the amount of remaining time the player has in
minutes
If the player is jailed forever, then it pulls from the language file
`jailedforeversign` property.
This will prevent overriding inventories in cell chests. When we tell
them the destination cell already has a prisoner in it, we try to find
the first empty cell in that jail but if all the jail's cells are full
then we tell them that as well.
