Visualize elevation profile for any line string or polygon

[ThomasHalwax]

After introducing terrain / elevation data with #41 the next step would be the visualization of elevation profiles for linestrings and polygons:

• user selects any measurement or linestring-based (bearing, route, boundary, ...) or polygon-based (area) symbol
• users clicks on "generate elevation profile"
• the elevation profile should be displayed

Examples:
RechenRaum VOIBOS
How to draw elevation profile for your path
OpenLayers Extensions Elevation Profile