Change abstraction level for map functions

This commit should have no functional affect. It just changes the
abstraction level of OpenLayers from completely abstracting away
getMapExtent etc, to using OpenLayers's functionality directly but
providing proj and unproj to make projections palatable.

app/views/changeset/_map.html.erb

@@ -80,9 +80,9 @@
     selectControl.activate();
 
     <% if ! @bbox.nil? %>
-      setMapExtent(new OpenLayers.Bounds(<%= @bbox %>));
+      map.setExtent(proj(new OpenLayers.Bounds(<%= @bbox %>)));
     <% else %>
-      setMapExtent(bounds);
+      map.setExtent(proj(bounds));
     <% end %>
   }