Allow more instances of small wonders and unique units

[Corbeau-1]

Create something like unique = 3 field for units and wonders (and buildings?) The number depicts how many instances of the thing can be produced.

unique = 1 mimics previous behaviour for wonders and unique units.

unique = 3 for, say, Pyramids, means that a player can have Pyramids in 3 cities.

unique = 0 means "infinite", meaning there is no limit of how many of X can be built.

Addition/extension/complication

Allow negative numbers as a code for "per X cities". So, unique = -5 would mean that one thing can be built for every 5 cities the nation has.

[jwrober]

i think this should apply to units as well.

[Corbeau-1]

Just a random thought, while I'm here: with this, the whole "Genus" thing can be abolished. Simply, small wonders have unique = 1 while regular buildings have unique = 0. Same for non/unique units.