json or geant4UI

[flagarde]

As i will need to dig into the code would you like :

1. stay with json
2. move back to UI
3. both

[ggrenier]

Option 3.
We have to stay with json so the scripts by Guillaume still works.
Having some parameters settable by the UI is still good when playing interactive.

JSON and UI don't need to cover the same parameters.
UI would more be intended for test/debug/play and JSON for "production"