Resolve "Decoration Observable warnigs lack Observable's expression"

Release notes

Improved information content of error messages of some Observables in CAFxAODUtils (CPDecoration, IPDecoration and other TQIParticle* Observables) Fixed some missing break statements in TQDefaultPlotter possibly messing up some types of plots and causing (justified) compiler warnings (fallthrough)

Details

added the Observables' expressions and active expressions to error messages issued if the container used by the Observable does not contain the expected elements, i.e., usually if it's empty.

The compiler warnings were due to missing break statements between different types of plots in TQDefaultPlotter which would have caused, e.g., requesting heatmaps to also invoke the segments for migration and contour plots...

Closes #308 (closed)