Core/Battlegrounds: Implement mercenary system

Port From (https://github.com/TrinityCore/TrinityCore/commit/87723e32e24f03ac1d062e33edcbe935e4e59421)

Source/Framework/Constants/BattleGroundsConst.cs

@@ -88,6 +88,10 @@ namespace Framework.Constants
         public const uint SpellAuraPlayerInactive = 43681;                // Inactive
         public const uint SpellHonorableDefender25y = 68652;                // +50% Honor When Standing At A Capture Point That You Control, 25yards Radius (Added In 3.2)
         public const uint SpellHonorableDefender60y = 66157;              // +50% Honor When Standing At A Capture Point That You Control, 60yards Radius (Added In 3.2), Probably For 40+ Player Battlegrounds
+        public const uint SpellMercenaryHorde1 = 193864;
+        public const uint SpellMercenaryHorde2 = 195838;
+        public const uint SpellMercenaryAlliance1 = 193863;
+        public const uint SpellMercenaryAlliance2 = 195843;
     }
 
     public enum BattlegroundEventFlags

Source/Framework/Constants/PlayerConst.cs

@@ -77,6 +77,10 @@ namespace Framework.Constants
 
         //Warmode
         public const uint WarmodeEnlistedSpellOutside = 269083;
+
+        //Mercenary System
+        public const uint  SpellMercenaryContractHorde = 193472;
+        public const uint SpellMercenaryContractAlliance = 193475;
     }
 
     public struct MoneyConstants

Source/Framework/Constants/Spells/SpellAuraConst.cs

@@ -510,8 +510,8 @@ namespace Framework.Constants
         Unk486 = 486,
         CosmeticMounted = 487,
         Unk488 = 488,
-        Unk489 = 489,
-        Unk490 = 490,
+        ModAlternativeDefaultLanguage = 489, // NYI
+        SwitchTeam = 490,
         Unk491 = 491,
         Unk492 = 492,
         Unk493 = 493,