Proposal: description_list as default of elements_names of each channel

[Nicogene]

After #161 is possible for each channel to specify the elements_names. I would put as default not the empty vector but the names specified in bufferConfig.description_list since usually it contains the list of joint names (e.g. in telemetryDeviceDumper)

cc @AlexAntn @traversaro @GiulioRomualdi