Extension of metadata section for generation of ISO metadata.
Merge branch 'roipac' of https://github.com/rudigens/ASF_MapReady into roipac

Conflicts:
	src/write_hdf5_xml/write_hdf5_xml.c
Merge pull request #209 from rudigens/roipac

Fixed the browse image problem. Found an issue with incidence angle metadata. Added extent section.