GeoPackage: Spatial Index reading
Geopackage: Spatial Indexing in Gp Process
GeoPackage: add file and class headers
Merge pull request #637 from NielsCharlier/geopkg_index

Geopkg: Spatial Indexing
Merge pull request #636 from NielsCharlier/geopkg_headers

GeoPackage: add file and class headers