NEMO support, additional fitting options, law updates (#61)

Fix generator software dependencies (#43)

* refactor shared methods for better code readability

* removed unused parameters from tasks

* add plotting task for generic splitted quantities

* config and label changes

* fix loaded herwig software

* fix LCG stacks

* update LCG stack

* update container OS to Alma9

* remove CentOS7 support

* build rivet analyses based on OS version

First stable version supporting Herwig7 and Sherpa MC event generators