Fix: nicely deal with concurrent modification exceptions that happen (rarely, if a player quits at the exact time the list is being checked)

* Gives a "high" level debug message & skips this particular scan.
Major: add actions (Command, Damage, Message, PotionEffect & Sound) similar to OtherDrops

* actions occur on each OB cycle so "ticks" setting makes a difference
Fix: commands should check "ob" not "od" & correct permissions to lowercase
Fix: damageaction shouldn't parse "damage" parameter as this is used by the boundary.