Changed GPS coords to reflect marina location

[crvogt]

Changed GPS coordinates to reflect location, La Spezia, Italy as per issue #23 Related to PR osrf/vrx#225

 <spherical_coordinates>
      <surface_model>EARTH_WGS84</surface_model>
      <world_frame_orientation>ENU</world_frame_orientation>
      <latitude_deg>44.091722</latitude_deg>
      <longitude_deg>9.823564</longitude_deg>
      <elevation>0.0</elevation>
      <!-- For legacy gazebo reasons, need to rotate -->
      <!--<heading_deg>180</heading_deg>-->
    </spherical_coordinates>

Modified goals in station_keeping task

<!-- Goal as Latitude, Longitude, Yaw -->
      <goal_pose>44.088427 9.8238729 0.0 </goal_pose>

Modified goals in wayfinding task

<!-- Goal as Latitude, Longitude, Yaw -->
      <waypoints>
        <!-- Approx. starting point of wamv -->
        <waypoint>
          <pose>44.0883705386 9.82367673319 1.21756121843</pose>
        </waypoint>
        <!-- A waypoint -->
        <waypoint>
          <pose>44.0916341743 9.82668230867 1.0</pose>
        </waypoint>
        <!-- Another waypoint -->
        <waypoint>
          <pose>44.0913208285 9.82350874434 1.0</pose>
        </waypoint>
      </waypoints>

Added wamv_gps.xacro to new directory, cora_description/urdf/sensors, to modify robot GPS coords and preserve VRX wamv coords.

Tested all tasks again, appear to operate as expected.