Expand the text for empire size unhappiness

[lmoureaux]

Improve the city dialog tooltip text that explains how many citizens are
unhappy because of the number of cities. Write two paragraphs: the first
describing the rules for the current player, and the second the status of the
city at hand. The total number of citizens that can be made content without
improvements is also shown; see #269.

Example texts

classic, size 14, communism

All cities start with 4 content citizens. Once you have more than 12 cities, a citizen becomes unhappy.

You have 36 cities, resulting in a maximum of 3 content citizens. In this city of size 14, 3 citizens are content.

classic, size 2, communism

All cities start with 4 content citizens. Once you have more than 12 cities, a citizen becomes unhappy.

You have 36 cities, resulting in a maximum of 3 content citizens. In this city of size 2, all citizens are content.

Aviation, size 4, monarchy

All cities start with 4 content citizens. Once you have more than 10 cities, a citizen becomes unhappy. Afterwards, for every 9 additional cities, a content citizen becomes unhappy. If there are no more content citizens, an unhappy citizen becomes angry instead.

You have 11 cities, resulting in a maximum of 3 content citizens. In this city of size 4, 3 citizens are content. With 9 more cities, a content citizen would become unhappy.

Aviation, size 2, monarchy

All cities start with 4 content citizens. Once you have more than 10 cities, a citizen becomes unhappy. Afterwards, for every 9 additional cities, a content citizen becomes unhappy. If there are no more content citizens, an unhappy citizen becomes angry instead.

You have 11 cities, resulting in a maximum of 3 content citizens. In this city of size 2, all citizens are content. With 18 more cities, a content citizen would become unhappy.

[jwrober]

I compiled this to see it in game. It looks great so I am in approval.