Difficulty settings

New features:

• Added "Threat timer" setting (ability to change how long it takes for the hourglass to turn)
  
• Added difficulty setting (affects starting stats for enemies)
  

Balancing:

• Increased AoE cap to 7
  
• Boss clears bad stacks when moving
  

Fixes:

• Fixed input rebinding not being saved
  
• Changes to stored window size management, attempting to prevent crashes and strange window position offsets
  

Misc:

• Added a new gamepad mapping
  
• Implemented updated Steam SDK
  
• Upgrade Defold to 1.10.3