Update URDF examples

[bmagyar]

Following #27

[destogl]

Find/Replace All didn't work perfectly in all cases.

Can you also add one more example showing the "user-friendly" joints?

1.1 Industrial Robots with only one interface - user-friendly Joints

The `ros2_control_components/PositionJoint` Joint is "position" command and state handles.


  <ros2_control name="RRBotSystemPositionOnly" type="system">
    <hardware>
      <classType>ros2_control_demo_hardware/RRBotSystemPositionOnlyHardware</classType>
      <param name="example_param_write_for_sec">2</param>
      <param name="example_param_read_for_sec">2</param>
    </hardware>
    <joint name="joint1">
      <classType>ros2_control_components/PositionJoint</classType>
      <param name="min">-1</param>
      <param name="max">1</param>
    </joint>
    <joint name="joint2">
      <classType>ros2_control_components/PositionJoint</classType>
      <param name="min">-1</param>
      <param name="max">1</param>
    </joint>
  </ros2_control>

[bmagyar]

@destogl thanks for the feedback. I've updated your suggestons to not add minmax where they werent originally.

[bmagyar]

I'd also prefer to not have the simple helpers in here yet. Theres a lot to implement first. perhaps a new page with extension proposals?

[Karsten1987]

are we having a follow up ticket to this for updating the parser?

[Karsten1987]

Also, shouldn't we rename classType to something else? what about just naming it plugin similar to what the gazebo tag is using?