2.0-0

* Changed the name to RSPARQL.

* Processing XML results is faster.

* Return the data frame directly, not as a list() with result and namespaces. 
  namespaces are now an attribute.

* Fix the case where there is a single variable returned and it is not structured as a data.frame, but a
  vector/matrix.

* Handle the case where the SELECT clause refers to variables not defined in the WHERE clause.
  Create a column of NAs.

* Allow the caller to use the namespace abbreviations in the result, rather than the complete URI.

* Automatically add PREFIX commands to the query by detecting the prefixes within the SPARQL query code
  and matching them to the namespaces provided by the caller (and the common namespaces).

* Catch Bad_Request errors and raise an error displaying the error message from the SPARQL server explaining
  the problem with the query.

* Functions to query the meta-data of the schema of the SPARQL endpoint.
  getClasses(), getTypes(), getPredicates(), getPredicatesByClass(), getClassPredType().

* Method to display the meta-data for the SPARQL schema.



