CartoDB: Implement TestCapability() so that CreateDataSource() actually works

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@28078 f0d54148-0727-0410-94bb-9a71ac55c965
CartoDB: accept a user column to have the same name of the FID (cartodb_id)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@28079 f0d54148-0727-0410-94bb-9a71ac55c965