"Get metadata" menu item only works for EML 2.0.0 documents
Currently the "Get metadata" function only works for EML 2.0.0. The version is
hardcoded in the code, but instead it should be determined from the namespace of
the EML document and then used to lookup the appropriate XSLT stylesheet to be
used. This is a fairly straightforward change, but EML200DataSource needs to be
extended to provide access to the namespace information.