new mechanism for RDF generation/import

[kohlhase]

We want to read RDF XML back in, that means we cannot use the templating engine to generate the XML. Instead we decorate

• the <concept> element in a KannSpec with a rdftype="o:foo" attribute, this generates a RDF triple of the form <rdf:type rdf:resource="o:foo"/>.
• the <field> element with a ```rdfpred="o:bar" attribute, this generates an RDF triple
  • <o:bar>baz</o:bar> if the type of the field is text
  • <o:bar rdf:resource="#ref#"/>, if the type of the field is reference and #ref# the value of the reference.
  • <o:bar>#val#</o:bar> if the type of the field is select and #val# is the value of the chosen option.
  • <o:bar rdf:resource="#obj#"/> if the type of the field is select and the chosen option carries an attribute rdfobj="#obj#".
    This should cover all the cases.

[kohlhase]

I have already extended schema/kannspec.rnc accordingly an updated the KannSpecs omdoc-annotations.xml and olia.xml. The KannSpec stanford.xml was never complete, see #16

[tkw1536]

@kohlhase I am almost done implementing the export. Because javascript has non-optimal handling of case-sensitive elements, it took a bit longer. While I was at it, I updated the export sample to pass the RDF validator at http://www.w3.org/RDF/Validator/ .

Note that this is only on the dev branch because @sourabhlal code isn't stable enough for a merge to master.