Initial draft of RDF-friendly SKOS importer
Add more SKOS bits, and handle (lack of) language more gracefully
Merge branch 'master' into skos-importer2
Ensure there are no loops in broader/narrower relations
Convert the vocab import to use *just* the OWL API.

This removes the non-Maven dependency on java-skos-api.
Add a test file
Various changes to match the behaviour of the existing SKOS importer.

Many bugs remain:
 - unicode problems - I am not sure unicode is working at all
 - wp2 keywords file is returning an empty ontology
 - extraction of lat/long is extremely dubious
Switch to Jena for parsing RDF due to bugs with OWL API.
In-progress work on Jena SKOS import and fixing resulting fallout.

SKOS import with Jena seems to work fine (rough edges notwithstanding).
Unfortunately, Jena comes with Xerces that has subtle differences to
the reference (Sun) SaxParser that got used previously. This has broken
some of the SAX-based importers. One fix involved using the qName of
attributes instead of the localName (which is apparently blank when
not using namespaces). This leaves an outstanding problem with whitepspace
around entities and an as-yet undetermined problem with some WP2 stuff.

As a move toward a fix, the SaxXmlHandler now implements the LexicalHandler
to be notified of entity events. Hopefully this will help in determining how
whitespace is being stripped and where.
Ignore WP2 tests for the time being (since they're being worked on).
Fix for whitespace handling when using Xerces parser.

 - Use a StringBuilder for concatenating the char buffer
 - Don't remove whitespace-only char strings because these become
   significant when they have a set of chars on one side and an
   XML entity (e.g. a quot) on the other
 - Normalise whitespace with StringUtils before its added to the
   graph.
Rationalise some model functions related to auth sets and vocabs
Various improvements to Jena SKOS importer
Fix localName being blank problem on WP2 handler
Reorganisation and cleanup of SKOS import classes and resources.
Ensure attribute is fetched an namespace stripped
Add test for OWL API file, and test idempotent import
Rename existing SKOS XML importer, add tests
Make SkosImporter API immutable and allow setting default language
for literals.