Added lookup fallbacks and strict mode
Added an explicit --strict mode flag, which will abort for non standard conformant files. The default is a non strict mode, which attempts to extract the attached XML with the help of multiple fallback mechanisms (which will be logged on the --verbose mode).
The file name of the XML file is now determined from the /Metadata XML, which falls back to "factur-x.xml" or "xrechnung.xml" in non strict mode and then to any ".xml" file.
If no /AF array exists or no XML invoice is found there, /EmbeddedFiles is searched as an additional fallback in non strict mode.
The attached binary is built for x64 Windows platforms (this binary is now also backwards compatible with Windows 7)