[Rivet] Removals for 2.0.0

[Andy Buckley]

I would like to remove the current "obsolete" analyses (i.e. notes which
have been superseded by papers) from Rivet for the 2.0.0 release: any
objections?

Also, can we remove the Multiplicity projection? I only added it all
those years ago as a demo of how a projection works, and it's only used
by the EXAMPLE analysis and a trivial call to it in ALEPH_1991_S2435284.
Typically it can be replaced, more clearly, by particles.size() ;-)

Andy

-- 
Dr Andy Buckley, Royal Society University Research Fellow
Particle Physics Expt Group, University of Edinburgh / PH Dept, CERN