Dev/fixing mesh filter tutorial

[micat001]

Description

Please explain the changes you made, including a reference to the related issue if applicable
Issue: #835

The mesh_filter tutorial was not running as written, and the text is misleading.
Lots of references to "point clouds" but the filter operates on, and publishes, depth images.

• I've updated the launch files to use the Panda, which is used extensively in other MoveIt tutorials.
• I've added working launch files that spawn a Panda arm + Gazebo + Controllers + RViz and another file that launches the mesh filter.
• I've updated the docs to replace the pictures/gif with Panda versions.

Checklist

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