Core/Scripts: Add/Update/Remove some DK SpellScripts
New Scripts:
Unholy Blight

Updated to 6.x:
Anti-Magic Shell
Blood Boil
Death and Decay
Death Coil
Death Pact
Death Strike
Icebound Fortitude
Vampiric Blood
Will of the Necropolis

Deprecated and removed Scripts:
spell_dk_anti_magic_shell_raid
spell_dk_anti_magic_shell_self
spell_dk_anti_magic_zone
spell_dk_blood_gorged
spell_dk_butchery
spell_dk_death_strike_enabler
spell_dk_improved_blood_presence
spell_dk_improved_frost_presence
spell_dk_improved_unholy_presence
spell_dk_necrotic_strike
spell_dk_pestilence
spell_dk_presence
spell_dk_rune_tap_party
spell_dk_scent_of_blood

TODO:
spell_dk_death_gate
spell_dk_death_grip
spell_dk_ghoul_explode
spell_dk_raise_dead
spell_dk_scourge_strike