Add GDALGeorefPamDataset and GDALJP2AbstractDataset classes and use them in JP2KAK, JP2ECW, JP2OpenJPEG and JPEG2000 drivers so that PAM georeferencing consistently overrides internal georeferencing; improve JP2OPENJPEG to be able to encode GCPs in a GeoJP2 box (#5279)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26571 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx