WFS: for WFS paging, change default base start index to 0 (was 1 before), as now clarified by OGR. Make the base start index configurable for servers such as MapServer 6.0 or 6.2 that still use 1 as the first index (#4504)

git-svn-id: https://svn.osgeo.org/gdal/trunk@25439 f0d54148-0727-0410-94bb-9a71ac55c965