Consider replacing Tesseract URDF version property with XML namespace

[marip8]

We should consider using a URDF namespace rather than a version tag for tesseract-specific URDF elements. URDF already has a version tag, so it's a bit confusing (and feels unnecessary) to specify an additional tesseract_version property.

Here's an example of what this might look like:

<robot name="my_robot" xmlns:tesseract="http://github.com/tesseract-robotics">
  ...
  <collision>
    <geometry>
      <tesseract:convex_mesh file="" convert=""/>
    </geometry>
  </collision>
  ...
</robot>

[Levi-Armstrong]

@marip8 Do you have time to work on this? I think this might be good to get into the next release.