telemetryDeviceDumper: escape underscore in joint names

[Nicogene]

This is a low priority activity, but the underscores are processed by MATLAB as subscripts, then we have to insert the escape character if we want to print them plain

See #87 (comment)

[traversaro]

Shouldn't this be handled by the code that plots the legend in MATLAB? Because the escaping rules are something MATLAB-specific, and may not apply if I plot the data and the legend on Python (for example).

[Nicogene]

Good point I didn't think about python