Backport AI and combat improvements from wotlk branch

[cala]

Bots have better management of:

• healing
• DPS
• Buffing Bots can now:
• Dispell (mage and magic for priest are WIP)
• drink/eat (not 100% working yet)
• pull mobs (not 100% working yet)
• Use elemental resist orders
• wait before engaging ennemies, letting some time to the tank for building up its aggro
• save/restore their combat order (you must update your character DB for this)