[freeciv-data] natural city names changed

I've just committed a patch that dramatically changes the way natural city
names are being handled.

Now you can link terrain with city names by adding parantheses and the
name of the terrains to look for or ignore. You can use ! to indicate that
the city should not be built near given terrain. Examples:

	"Dovre (!ocean, mountains)"	will be built near mountain but
					not near ocean
	"Bergen (ocean)"		will be built near ocean
	"Babylon (river, desert)"	will be built where there is
					both river and desert nearby

Since this way of doing it is so different from the way it used to be,
we've had to remove the previous natural city names ruleset setup. This
means there currently are no nations with natural city names.

I don't think merely converting from the previous data to the new way of
doing it would be right, since we now can mark city names more precisely
(ie with multiple terrain names, and also exclude terrains). So what we
need now is for someone to sit down, work through maps or their
photographic memories, and mark up the nation ruleset cities again.

To those who just recently submitted nation patches: Please change your
patches to conform to this new way of doing natural city names, and submit
new patches.

Yours,
Per

Ask not what you can do for your country
Ask what your country did to you
 -- KMFDM, Dogma