Core/Units: moved health and power ordering predicates from Unit header into CommonPredicates

Port From (https://github.com/TrinityCore/TrinityCore/commit/2f6ed2c203b16a1d1e85f61a8b8e2cf3d1a4e784)

Source/Scripts/Spells/Item.cs

@@ -7,6 +7,7 @@ using Game.BattleGrounds;
 using Game.DataStorage;
 using Game.Entities;
 using Game.Loots;
+using Game.Miscellaneous;
 using Game.Scripting;
 using Game.Spells;
 using System;