Added SpellDamageAoe class that supports Arcane Explosion, Consecrate, Hellfire etc.
Converted FanOfKnives into SpellDamageAoe and removed resulting duplicate tests.
Converted Swipe to SpellDamage class, named tests, added Spellpower test.
Combine HolySmite and Fireball tests into a SpellDamage test since these completely overlap. Added Spellpower test.
Convert HolyNova to SpellDamageAoe
Move Backstab's targeting logic to use canBeUsedOn. Renamed and organized tests.
Use CanBeUsedOn.
Move CanBeUsedOn targetting logic into SpellCard. Renamed SpellDamageAoe flag to avoid confusion.
Move target validation into CanBeUsedOn and/or flags.