DB/NPC: Argent Cannon

Add the regen mana on spell casted, and set initial mana to 0.
Closes #15460

sql/updates/world/2015_09_07_05_world.sql

@@ -0,0 +1,5 @@
+--
+DELETE FROM `spell_linked_spell` WHERE `spell_trigger` = 57387;
+INSERT INTO `spell_linked_spell` VALUES (57387, 57608, 0, 'Argent Cannon - Powering Up The Core');
+UPDATE `creature` SET `curhealth`=126000 WHERE `id`=30236;
+UPDATE `creature_template` SET `unit_flags2`=0, `RegenHealth`=0 WHERE `entry`=30236;