(campaign branch) shipyards should be disabled in normal games

[Nasenbaer]

Similiar to the barbarian weaving mill, the shipyard should be disabled in normal games, as long as it has no real use.

[SirVer (sirver)]

I solved this by using wl.game.Players.forbid_buildings{"shipyard"} in all starting conditions of the atlanteans; a forbidden building does not show up anywhere in the game and is therefore like one that can't be build. So the technical implementation is different to the barbarian weaving mill (this one can never be build, as long as the conf file is not changed), but the result should be the same.

I set this to fix committed as it was against the campaigns branch and the fix there is in r5639.

[SirVer (sirver)]

Released in build16-rc1