Double PMT ap probability for photons emitting double PE.

[zhut19]

What is the problem / what does the code in this PR do
The double photo-electron in PMTs also contributes to generating PMT afterpulse, in this pr, we store a boolean array noting photons emitting dpe, in the last step of generating S1s and S2s. While we double the PMT AP probability for those photons when generating PMT afterpulses.

[coveralls]

Coverage decreased (-0.02%) to 81.459% when pulling 182c9fd on ap_by_dpe into f917fb5 on master.

Pending syntax fix

[hoetzsch]

Hey @zhut19,

thanks for the fix, now the population with the additional delay is gone!
The first plot below shows the ratio of the He afterpulse rates I get from the wfsim data after and before the DPE fix, and it turns out to be close to the dpe probability, so this seems to work well.

I still can't quite reproduce the afterpulse rates from the input file though, but the discrepancy has decreased significantly with the DPE addition, from -33% to -18%, shown in the second plot. Still not sure where this comes from, could be pile-up. But I don't think it's related to the DPE thing.

[terliuk]

It seems like it does what this PR is supposed to do, so let's merge it and figure out why there is still remaining mismatch separately.

[ramirezdiego]

Agreed