Star Explorers Testing Branch Updated to Pre-Release Version 0.2.0

There are a bunch of small fixes and updates in this latest build.

• The Alien City got a better exterior model.
  
• Footsteps in the alien city will no longer sound like gravel.
  
• Caves - stalagmites and stalactites will no longer get the player stuck!
  
• I made them passable now, since they were never really intended as barriers. The big, hallway-blocking stalagmites and stalactites will still function the same way, but the smaller, individual ones will no longer be a burden.