Also:
- Use a scroll pane for the credits in the about dialog, so that new credits can be added without altering other elements
- Use a scroll pane for the list of sections to be deleted in the resize outdoors dialog
- New cContainer superclass for controls that contain other controls
- Scrollbars consider their maximum as part of their state
This includes the following changes (mostly related to the above):
- Move loc_compare functor to location.hpp
- Add reattach() function to rebind a town or outdoor section to a different scenario object. (I don't think this is strictly necessary, as the scenario reference is only used in limited situations in the game itself, not in the editor, but it's better not to keep a reference to freed memory around when importing a town or sector from another scenario, even if the reference is never accessed.)
- Fix imported towns not being officially "loaded" until you explicitly use Load a New Town to reload them
- Fix Choose button in Load New Sector dialog
- More functions in the vector2d implementation
