Scripts/Ulduar: Spellscripts for Mimiron

Cutting the commit in pieces, so that the diff can be viewed on github...
This script can be replaced by spell_linked_spell
(64626, -SPELL_FROST_BOMB_LINKED, 0, 'Explosion - Remove SPELL_FROST_BOMB_LINKED from caster'),
(64626, -SPELL_FLAMES_PERIODIC_TRIGGER, 1, 'Explosion - Remove SPELL_FLAMES_PERIODIC_TRIGGER from targets');