Merge pull request #521 from melissalinkert/may-bug-fixes

Assorted bug fixes for May
CellWorxReader: Reuse OMEXMLService
Remove unused ome.xml.model.OME imports
xsd-fu: Issue a warning if genshi is not available

It's a bit more informative than an exception.
Merge pull request #505 from rleigh-dundee/metadataroot

Add MetadataRoot to MetadataStore getRoot/setRoot interfaces
merge develop -D org -I include -E exclude: PR 524 (xsd-fu: Issue a warning if genshi is not available)