Core/Spells: Update Periodic System to 6.0.2

TODO: Implement the new way haste affects ticks and check up on existing scripts.
Find out if they by multipliers mean that all % done bonuses are recalculated on each tick or some are and some are not...

"Periodic damage and healing effects now dynamically recalculate their damage, healing, Critical chance, multipliers, and period on every tick."
Ref: http://www.wowhead.com/news=243670/official-patch-notes-for-patch-6-0-2-the-iron-tide-and-warlords-class-tuning-cha