Fixed terrain flattening bug caused by sub-building metro station having no visual model (it shouldn't need one, it is inside the station, isn't it?)

Fixed missing metro spawn point.

Updated to native sub-building support.

• fixed spawn points for local trains
  
• fixed regional trains not using the station
  
• fixed the station didn't respect the train station milestone
  
• added support to place train and metro stops on any station without Multi-Track Station Enabler
  
• changed m_fixedHeight to true

A huge thanks for BloodyPenguin for adding spawn points to the station! This solved all problems everyone was so upset about! Also thanks about helping me to get the milestone working.

initial release