UIGlobals: expose FormatSettings

Expose the FormatSettings structure to allow access by the lower
layers of software to user settings
Use new UIGlobals for dlgWaypointEditShowModal

Switch to the lighter-weight and global API to access the coordinate
format selected by the user
GeoPointDataField: make format const
GeoPointDataField: add method GetFormat()
Form/DigitEntry: Extend editing of waypoints to all lat-long formats

UTM yet to be supported