Herwig7_i: Clean-up of Herwig7 implementation in Athena

As part of this QT all historic jO fragments / config scripts from Herwig7.0.x were removed and jO fragments for Herwig7.1.x and 7.2.x were harmonised where possible (see this closed MR, which somehow ran into a dead-end), also the agreement of the ATLAS default settings with ATLAS common parameters and Hewig7 default tune /setup was checked.

We did some initial tests with some JO's to test the changes. After the changes have propagated into a release, we will do a full validation of the changes using the standard Herwig7 validation samples