Building::crops_grown is now std::vector<Crop_amount>.  Building::get_empty_fields() adjusted accordingly.
In City::add_open_area(), if the area is a farm then we populate area.building.crops_grown with a list of the crops available in the Map_tile the farm is on.  Of course, 0 of each crop is grown.
Right-align a couple fields.
More Interface::minister_food() work.