GML: add support for reading Finnish National Land Survey Topographic data (MTK GML)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26140 f0d54148-0727-0410-94bb-9a71ac55c965
ogr2ogr: add -addfields option to add new fields found in a source layer into an existing layer ; add -unsetFieldWidth option to unset field with and precision; add -dim layer_dim option to force the coordinate dimension of geometries to match the one of the layer geometry type

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@26141 f0d54148-0727-0410-94bb-9a71ac55c965