AI Update

This is a small update with some AI fixes, just in time to take a break over the holidays to wander through the campaign. Perhaps even invite some friends.

• Fixed Strider Hub eventually not working. The AI forgot that striders can move, so was not able to reuse open space to place additional strider nanoframes.
  
• Increased the placement distance between Solar and Wind Generators. This makes the AI much less likely to block its base on maps with narrow passes.
  
• Construction delays for Easy, Normal and Hard now reduce to about 75% their maximum after about 20 minutes. This causes the AI to ramp up slightly in the lategame.
  
• Reduced initial construction delay for Hard, to make it slightly harder early on.
  
• Fixed an inverted comparator which was causing AIs to make Solars (rather than Singus) in the late game.