Factored out the map object creation

Since I want to re-draw the map objects when we come back to the
MapViewController, I factored out the code that queries the database and
creates the map objects for overlay on the map.  Now that code is called again
every time that the viewWillAppear method is called by the system.  This means
that if changes are made to the filter, the redrawing will happen
automatically.
Added the auto-center on GPS setting

Added the UISwitch on the Settings scene to toggle whether the map will
auto-center on the GPS.

Also changed the method that SettingsViewController overrides to detect when
the view is being switched away from, which is when the ConfigModel is
committed to the UserDefaults.
Added vim modeline