v0.1.0.22 - Trading addition

Haven't updated the demo for a while, as i've been mainly focused on scenario features that are only in the early access version on Steam. However now trading has been added, thought id update the demo for people to check out. 

Once an airlock is built (with sufficient docking clearance), the station computer trading beacon becomes available. Once enabled passing traders will visit from time to time. Once a trader is docked, clicking on them will bring up a trading board where resources can be traded. Currently air, fuel and metal can be traded at the buy/sell price. You have to have a positive amount (green) for the transaction to be accepted.

Lots of bug fixes and improvements as well, enjoy!