support for reading meta data and auto filter from Excel 2003 XML

Gnumeric currently ignores meta data (e.g. author and title) and auto filter settings when importing Excel 2003 XML file.

The attached excel_xml_metadata_and_auto_filter.patch provides support for common meta data and basic auto filter settings.

See also sample.xml for a sample file generated by Excel 2016 (+ xmllint -format).