Additional Refactor Voronoi

.. updated to have a more Qt/C++ friendly interface:

    Voronoi *test = new Voronoi();
    test->addSite(QPointF(2,5));
    test->addSite(QPointF(3,2));
    test->addSite(QPointF(6,4));
    test->run(QRectF());
    delete test;

    the output is still written to standard out as a
    series of points, lines, vertexes and edges. This
    was to enable validation against the original
    c program.

.. whilst the original functionality is now embedded a
   further update will need to convert the output into
   a vector of lines to draw.

   will do this as part of adding it to a plot as an
   annotation.