Buffed the Thermae tradition into 'Bread and Circuses' - now it also gives +2 food on happiness buildings.

Tentatively buffed the Princeps Civitatis to +10 Production -10 Happiness. This may be way overtuned in the production department but I wanted to make the Happiness effects harder to deal with, felt like I was dealing with them a touch too easy. This is the third iteration - it started at +/-5, released at +/-7, and now it's at +/-10. If this is too strong in either direction I might make it uneven like +5 prod -7 happiness.