Update Navigation Demo to Include latest URDF

 * Loads the latest URDF from euler_support package. 
 * Changes the urdf in two ways
     * Removes the prefix from the base_footprint frame, so when used in the macro, it appears as base_footprint, not vetex_base_footprint
     * Changes the origin of the S300 scanners to be at the laser scanner itself. 
 * Update the Navigation configuration to match the new URDF frame names for the S300 scanners. 
 * Updates the Stage simulation to reflect the true location of the lasers. 
  
[The frame of the sensor should be the frame of the laser scan](http://www.ros.org/reps/rep-0138.html). It could be made into a macro, but I don't think it is necessary.