Remove population bonus from most non-house buildings.

Houses increase the population limit. Various other structures did it too as a side-effect.
This changes that, making houses more unique.

This also removes the Gaul/Brit bonus that most buildings increased population, as they already build structures 20% faster and that is deemed a sufficient early-game advantage.

Accepted By: borg-

Differential Revision: https://code.wildfiregames.com/D2950