Fix interface between fullSimLight configurator and Geant4

When reading g4ui commands from the FSL config file, we need to make sure that the initialisation of the Geant4 kernel happens at the right time. This MR fixes this problem, by initialising the Kernel when it finds the first FSLgun command and before applying it.

added FullSimLight label

requested review from @dellacqu and @boudreau

assigned to @mbandier

approved this merge request

enabled an automatic merge when the pipeline for 11ba0ca6 succeeds

aborted the automatic merge because source branch was updated

added 1 commit

• d02b7331 - Clean the debug outpu

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merged

mentioned in commit 9fcfde8d