[Rivet] a few issues/problems with Rivet and its tools

[roman lysak]

  Dear Rivet authors,

in preparing the Rivet routine for the upcoming 13 TeV ATLAS min-bias 
analysis, we encountered the following problems with Rivet tools:

- concerning 'Histo2D' objects:
     - Rivet::Analysis::scale() --> seems it does not work (is not 
implemented) for Histo2D
     - yoda2root does not work for Histo2D: it seems 'yoda.to_root' is 
where it fails

- concerning Profile1D:
    - yoda2root does not work: after conversion it seems that all bins 
are zeros ( checking with TProfile::GetBinContent() and GetBinEntries() ).

It would be really useful if these could be implemented/fixed.

Thanks a lot,
   Roman

P.S. I'm using Rivet 2.2.0