Demo update 0.5.1 Some QOL improvement and bug fixes

The main feature of this update is improvements to the moose AI in relation to minecarts. They will now prioritise minecarts that already have gems or logs in them when selecting where to unload. And the moose can now unload to any minecart in the train, not just the very top one.

The rest of the patch notes follows below:

• Added missing upgrade images
  
• Improved save robustness
  
• Miners now prioritise minecarts that are already almost full when deciding where to unload gems or logs
  
• Miners can now drop off gems or logs to any cart in a minecart train
  

• Fixed UI and rendering not working properly after minimizing the game
  
• Fixed a bug causing the moose to stay in the air sometimes after being placed
  
• Fixed a bug causing the tooltips for grinder upgrades to show the wring values
  
• Fixed a bug causing the railway costs to not be in sync with each other
  
• Fixed a bug causing the add railway button to not be disabled properly after buying railway length on max setting
  
• Fixed settings not set to default when no settings file exists