Adapted Sherpa interface to support releases 2 and 3
Update CMake modules for Sherpa 3
Move CI to LCG_106a to pick up Sherpa 3.0.0
Modify CI to use Sherpa 2 for legacy builds
Implemented modification to use PHOTONS::AddRadiation function directly.
Removed unnecessary setting of blob status
Introduced finalise function inside EvtSherpaPhotons class to control the order of static destruction.
Updated setupEvtGen script for Sherpa 3