Reworked the export functionality of asf_export for HDF5 files. For the export it now expects to see an XML file that is most likely generated by the new write_hdf5_xml tool. That allows user to generate custom HDF5 files, as long as they stick to our XML structure. That part will still need to be documented.

Restored the meta2xml to its old functionality. Does not know anything about ISO structures and such anymore. All that functionality moved to write_hdf_xml.

The HDF5 generation of Seasat data still needs to be refactored. Commented the old code out for the moment.