[Spells] Update to mod incoming Spell Damage amount focus, SPA 297 and 484 to support focus from AA and items.

[KayenEQ]

Added support for modify incoming spell damage amount focus effects, SPA 296 and 483 to work on items and AA's.
These effects can be used to modify incoming spell damage by flat on a target with the buff containing the focus.
If you put it on an AA or an item you can cause your client to have an innate increase or decrease in spell damage taken by amount.
Example, your client gains an AA that makes them take 100 less damage from Fire Spells.
Positive value increases damage taken, negative value reduces damage taken by amount
These two foci do same thing and will stack with each other.

Also, removed some out dated uses of the spell that are no longer applicable.

SE_FcDamageAmtIncoming 297, Focus Effect,, On Target, damage taken flat amt, base: amt
SE_Fc_Spell_Damage_Amt_IncomingPC 484, Focus Effect, On Target, damage taken flat amt, base: amt