New editor commands: Resize Outdoors and Import Sector

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

src/scenedit/scen.townout.hpp

@@ -11,9 +11,11 @@ void edit_town_events();
 void edit_advanced_town();
 void edit_basic_dlog(short which_node);
 short edit_talk_node(short which_node);
-location pick_out(location default_loc);
-cTown* pick_import_town(short def);
+location pick_out(location default_loc,cScenario& scenario);
+cTown* pick_import_town();
+cOutdoors* pick_import_out();
 bool new_town(short which_town);
+bool resize_outdoors();
 void edit_placed_item(short which_i);
 
 void delete_last_town();