Area::Area() sets building's position.
Building now stores its position (if it came from an area, otherwise [-1:-1]).  New functions Building::get_name(), Building::get_job_citizen_type(), Building::get_upkeep().
New function City::get_all_buildings().  City::place_keep() uses the full Area constructor in order to set up keep correctly.
New function Interface::building_status(), for viewing and changing buildings.  Viewing is complete, no changing yet.
Complete redesign.