Rel val pythia8 update 7 4 x without tauola option

Replaces PR 6711 addressing comments from Josh. 
.GENSIM_update_7_4_X_merged into new branch for pull request to update Configuration/Generator only. Requested by Giovanni and Josh. added by nugent@physik.rwth-aachen.de
Since people will use these as examples, can you remove the external decays import from the non-tauola fragments?