- add checks for XMP specification
  http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/XMP%20SDK%20Release%20cc-2014-12/XMPSpecificationPart1.pdf
- add checks for IPTC specification
  http://www.iptc.org/download/download.php?fn=IIMV4.1.pdf
- add more testfiles


