Update to 2.8.0 - from Jaap Boender

2.8.0
* Improved NRLModel query prefix expansion.
* Support for plain SQL queries in the Virtuoso backend.
* Introduced new query language flag QueryLanguageSparqlNoInference.
  This language is not supported by any backends. It is supposed to
  be used in clients like Nepomuk to avoid the usage of long user
  types which are harder to read.
* Convert Virtuoso IRI_ID values into simple literal strings. At some
  point if the need arises we might call ID_TO_IRI() to convert them
  into URIs.
* New boolean option "noStatementSignals" in the Virtuoso backend which
  will disable Model::statementsAdded() and friends.
* Improved local unix socket communication in the server/client system:
  A custom socket implementation as a replacment for QLocalSocket makes
  it possible to use one socket across threads.

2.7.6
* Support for the new SPARQL 1.1 DELETE statement which omits the graph
  to delete from for faster removeAllStatement execution.
* Support for the new default graph query result format of Virtuoso >= 6.1.5
* Fixed apidox generation with Doxygen 1.8.0.

2.7.5
* Be less strict when converting a string to a QDateTime:
  - Allow an empty time part, ie. "2011-10-04".
  - Allow the usage of a space instead of "T" to separate date from time.
* Fixed URI parsing in the SparqlModel.
* Fixed an endless loop in the VirtuosoModel destruction which can happen
  in rare error cases.
* Fixed serialization of non-string literal values.
* Support Turtle result encoding in the SPARQL model.

(markd)