Add the wcs_virtds_params.py sample utility to be able to set the MapServer WCS virtual dataset parameters from a tileindex with rasters of mixed SRS (linked to MapServer RFC100)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26174 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' of github.com:rouault/gdal into trunk_with_coverage