V 1.8.0h - Minor changes

Thanks everybody for the feedback!

V 1.8.0h

Balance

• Revising the Past: Increased minimum threat from 4 to 5. Increased rarity from 3 to 4.
  

Bugfixes

• Fixed too many buildings being visible in the research tree due to the change in 1.8.0g (it was supposed to be only for upgrades!)