- Update to 0.17.0:
* set the baseline C++ version to 17.
* cleaned up the public API to replace pstring with std::string_view, union
with std::variant, and boost::optional with std::optional. With this
change, the public API no longer has dependency on boost.
* switched to using ixion::model_iterator for horizontal iteration of cells
instead of using mdds::mtv::collection.
* fixed a bug where exporting a spreadsheet document containing adjacent
merged cells regions to html incorrectly exported the merged cell areas.
* cached cell values are now correctly loaded from the xlsx file.
* utf-8 names are now allowed as element and attribute names in the sax parser.
* unquoted utf-8 property values are now allowed in the css parser.
* added yaml output option in orcus-json.
* fixed a bug where mapping of an XML document with namespace aliases
sometimes corrupts the alias values.
* added orcus.FormulaTokenOp enum type in python which describes type formula token
operator types in a more finer grained manner.
* added notes to how to use orcus-xml and orcus-json to map XML and JSON
documents to spreadsheet documents.