Core/Arenas: Drop old .modify arenapoint command, create a new command to add currency to players.

sql/updates/world/2012_11_22_00_world_command.sql

@@ -0,0 +1,4 @@
+DELETE FROM `command` WHERE `name` = 'modify arenapoints';
+
+INSERT INTO `command` (`name`, `security`, `help`) VALUES
+('modify currency', 2, 'Syntax: .modify currency #id #value\nAdd $amount (without precision) of $currency to the selected player.');