[Merge] Update and reorganisation of the examples in view of the Hackathon

This pull request provides up-to-date versions of the SPM and FSL additional examples available in the `examples` directory (e.g. `spm_results_2contrasts.png`).

No changes were applied to the model (i.e. `spm_results.provn` and `fsl_results.provn` are unchanged).

Each examples has now its own sub-folder `examplexxx`.