City growth more challenging

[MagicBuzz]

I'm not sure if it was already mentioned here, but here are some suggestion for realistic city growth.

Actually, why a city grow?

Three reasons:
- City is nive to live : near water, many tree arround, etc.
- City is well serviced, so people can travel and go work easily.
- City is wealthy and its industries needs a lot of people to work in.

Right now, it seems only the point 2 have influence on the growing rate.

For point way, why not counting the trees arround the city for 5 tiles width, then add the same for water (coeff x2). Divide it by current population, then you get a first ratio.

For second point, you already discussed about it, I won't suggest anything else.

For the third point, just divide the total amount of goods transfered from the industries owned by the city, by the population.

Next, you can combine these three ratios to get a much more realistic growth rate for the city, according 3 differents factors instead off only one.

You just have to find a realistic way to combine these 3 ratio, as they could be really different (first one will be alway less than 0, and last one could be much far more than 0 in no time).