Have stopped muons emit more protons for the tolerances study

[AndrewEdmonds11]

One of the suggestions in today's meeting that might require a change in the code is to have a setting so that we can assign how frequently stopped muons emit a proton.

I'll look into this and implement it soon.

[thnam]

I think some code similar to this is enough:
https://github.com/alcap-org/g4sim/blob/master/src/MyDecayPhysics.cc#L105-L118

[AndrewEdmonds11]

So I've had a look into this and I don't think that would be enough since the muon capture process is a bit more complicated than a simple phase space decay.

Currently, the muon capture process happens in Geant4 (G4MuonMinusCaptureAtRest::AtRestDoIt() and DoMuCapture()) which does the initial mu- + p --> nu + n process with the nucleons and then passes the resulting excited nucleus to G4ExcitationHandler for all the proton emission stuff.

We might be able to specify that we do capture 100% of the time rather than 60% by somehow setting lambdac and lambdad in G4MuonMinusCaptureAtRest but that would only be a small improvement.

At the moment, it's quicker for me to just re-run to get the necessary stats so I propose to put this on the back-burner for now.