KeeperRL Alpha 31 hotfix 2

This is another bug fixing patch.

• Fixed crash caused by inability to generate the "black rats" z-level.
  
• Fixed bad generation of some towns that made them embedded in mountain tiles.
  
• Fixed crash caused by team members being at a different site when in full control mode.
  
• Fixed entry to the "Adoxie feet" secret.
  
• Fixed crash caused by dual wielding a staff of suicide along with another weapon.
  
• Added an error message instead of crashing when the game can't find a texture file.
  
• Added a link to the game's github page in the main menu.