Pics for historical events

Hello!

I guess this is already known, but what the hell.

I just found that is possible to customize the pics shown in historical events (like archimedes_screw, eruption_at_etna, etc), by putting pictures with those names in the eventpics folder, under ui/culture.

So, for example, instead of that messenger guy we can have now an actual volcano image when the Etna explodes. For this, you only have to place an eruption_at_etna.tga in ui/roman/culture/, etc.

Right now I only have images for espionage_in_carthage and for crucifixion_at_golgotha ~:rolleyes:, but I'm going to add pictures for all the vanilla events, yay!