Update soprano to 2.3

* New class LanguageTag replacing the old simple string language handling
  with a sophisticated one implementing RFC 4647. At the same time Soprano
  now directly supports plain literals in addition to typed string literals
  (compare LiteralValue::createPlainLiteral).
  CAUTION: This patch changes behaviour: parsers and storage backends will
  now return plain literals instead of typed string literals!
* New static methods Node::resourceToN3, Node::literalToN3, and
  Node::blankToN3 for easy N3 formatting without the creation of a Node
  instance.
* Fixed both Node::matches and Statement::matches - now only the paramter
  is treated as a wildcard
* sopranocmd:
  - new paramter --file which allows to execute commands on files directly
    without creating a database on disk.
  - standard namespace prefixes rdf, rdfs, xsd, nrl, and nao are now added
    to sparql queries automatically if used.
  - construct and describe query results can now be serialized in all
    supported formats.
  - New parameter --index which allows to wrap an IndexFilterModel around
    the actual Model.
  - New command 'monitor' which allows to monitor a remote repository for
    statementAdded and statementRemoved signals.
* New class Graph which is a simple QSet based container for statements as
  a quick replacement for Model in case one wants to handle a small number
  of statements without query support.
* Fixed plugin loading on windows.
* Fixed a deadlock in the IndexFilterModel in case a query could not be
  parsed.
* Prevent Model::removeContext to remove empty contexts, i.e. the whole
  database.
* Statement::operator<<(QTextStream) now uses a simpler format (only spaces
  between nodes and no brackets)
* Updated Sesame2 to 2.2.4
* Added prefix handling to the Serializer API. For a future Soprano version
  the Serializer API has to be replaced with something more powerful.
* Improved inference rule handling in the rule parser

(markd)