This task is about adding the elevation property to Placemarks, Polygons, Paths and GroundOverlays in Marble. Take the UI file

http://devel-home.kde.org/~tackat/ElevationWidget.ui

and copy it into src/lib/marble.

- Add a Tab "Elevation" to the EditTextAnnotationDialog.

- Place the ElevationWidget inside.

- Extend the ElevationWidget so that it displays km, m, mi or feet in the Spinbox suffix depending on MarbleLocale settings and adjusts the values (possibly introduce a helper method for conversion inside MarbleLocale). Code might be borrowed from the MapScale plugin.

- Make sure that it's possible to change the elevation of placemarks. The elevation should be displayed correctly (try values for space e.g. 2000 km). Ensure that saving and loading the Annotation file still preserves the entered elevation value.