Online monitor standard plots

With this minor change, the user can define, for which tracking/clustering module he'd like to display the standard plots.

We should keep in mind, that for now this is rather simple. In case of including the TrackingMultiplet ( !273 (merged) ) this would probably mean, that an additional set of default plots would be defined, like ...

if(tracking_module == "TrackingMultiplet") {
  m_config.setDefaultMatrix("tracking", ...);
}