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. 
  
We generally prefix all frames in the macro so that multiple includes do not have colliding frame names.  For example, if we had multiple vetex platforms.  While it's not likely that we will have multiple vetex platforms in a single URDF, we might have multiple that share tf (i.e. multiple platforms controlled by a single ROS instance).  Under such a case, you would need the frames to be uniquely named.  Is there a compelling reason to change this?