spawn index needs to be restricted to not 0, 1 or 255. We need to check if it would impact an existing spawn

We need to reinforce the Player::SetSpawnMapAndIndex and Player::SetSpawnMap functions on these possible issues. If we overflow the int16 then we start back at 0, but 1 is already taken by the player.

#581 spawn index needs to be restricted to not 0, 1 or 255. We need to check if it would impact an existing spawn