Update sdo-visualartwork-examples.txt

Added missing Microdata and JSON example, and updated RDFa examples from most recent corrections at http://www.w3.org/wiki/WebSchemas/VisualArtwork
Update schema.rdfa with artEdition property

Added in missing artEdition property
Merge pull request #31 from lazaruscorporation/patch-1

Update sdo-visualartwork-examples.txt
Merge pull request #32 from lazaruscorporation/patch-2

Update schema.rdfa with artEdition property
Merge pull request #33 from danbri/sdo-visualwork

Bring in latest VisualWork improvements