Function PerformIngameSpawn

* Performs an in-game spawn and returns the [Creature] or [GameObject] spawned. * * @param int32 spawnType : type of object to spawn, 1 = [Creature], 2 = [GameObject] * @param uint32 entry : entry ID of the [Creature] or [GameObject] * @param uint32 mapId : map ID to spawn the [Creature] or [GameObject] in * @param uint32 instanceId : instance ID to put the [Creature] or [