0.80.0 - More Dakka

This is a feature release. Changes:

• You can now install weapons in all three weapon slots on K37.
  
• You can now sell your weapons.
  
• Upgrades were grouped by type, so now it's obvious if they replace each-other.
  
• Re-balanced reactor leaks.
  
• Relabeled "buy" buttons to "install" if upgrade does not cost money.