Add and convert tests for pythia

Summary:
Introduced new tests for PYTHIA interface and converted all previously existing tests
for decays simulated with PYTHIA into new json format.

This includes introducing new histograms in the new testing module test/testDecayModel.cc and a new functionality to produce histograms per daughter.
New json files were therefore introduced.

The CI test test/checkJsonFiles.py has been updated accordingly to support quark names.

This is related with !29.

Test Plan: Converted tests in this differential provide same histograms as the ones produced with the old framework.

Reviewers: tlatham, kreps, jback

Reviewed By: tlatham

Tags: #evtgen

Differential Revision: https://phab.hepforge.org/D129