Script/Spell: Apply Frost Imbued Blade only in 25 man mode

Note: Quest credit spells are already casted in 25 man mode only.
Script: Remove unnecessary constant
Remove BOM
Scripts/Pit of Saron: Changed Overlord's Brand script to be safer

Closes #9125
Merge branch 'master' of git://github.com/TrinityCore/TrinityCore.git