Change QoS for meshes in RViz display

[aock]

This is a follow-up of PR #34 . It was not able to visualize a mesh geometry from topic because my publisher had not the same QoS configuration than the RViz plugin's subscriber. To fix this, I added an option to change the QoS in Rviz. The configuration of PR #34 remains the default.

I tested it with the code of this repo: https://github.com/aock/mesh_msgs_examples