Reduce population of early houses

[2TallTyler]

Lowers early house population to make horse-drawn cart passenger transportation viable in early cities.

• 1700-1850: 1/4 population
• 1850-1950: 1/2 population

To Do

• Needs testing with gamescripts and town growth over time. If problematic, set parameter Off by default, otherwise turn it On by default
• Don't forget to change version number before merging