Experimental Balance Patch

I am pushing a balance update to the experimental branch. These are the main changes:

• Tech cost doubled

• Era techs no longer cost stability, but require 50% of previous tier techs/culture to be researched

• Culture tech stability gain from factions divided by four

The idea is to make it more necessary to diversify tech as well as to slow down the (especially stability) pacing, while preventing death spirals from happening in the early mid game.