Added OffScreenOpenGLRenderer. This off screen rendered is a new mode for...

Added OffScreenOpenGLRenderer.  This off screen rendered is a new mode for capturing images.  When OpenGL multisampling was added for antialiasing, the antialiasing did not work with QGLWidget::renderPixmap.  Anti-aliasing does work with this new off screen renderer.  This off screen renderer does work with the newer QOpenGLWidget but multisampling does not work with QOpenGLWidget so we remain using the deprecated QGLWidget.