Added parameters to set a .rviz configuration for the rqt_rviz plugin and disable the menu bar.

This addresses the question I posed on ROS answers:
http://answers.ros.org/question/98126/using-rqt_rviz-with-custom-rviz-config/

The parameters are local to the namespace rqt_rviz is run in, but not private. If I create a ros::NodeHandle object, the node name seems to come from rqt (like /rqt_gui_cpp_node_24524) and not the launch file so setting a private parameter from the launch file does not seem possible.