Added and changed some natives

Added Gamma_GetGameModeName
Added Gamma_GetPossessedPlayers
Added Gamma_GetPlayerBehaviours
Changed Gamma_GetAllGameModes to return a cloned array with the calling
plugin as owner
Changed Gamma_GetGameModeBehaviourTypes to return a cloned array with
the calling plugin as owner
Changed Gamma_GetBehaviourTypeBehaviours to return a cloned array with
the calling plugin as owner