Training examples initialization script

As part of the ongoin effort to unify/run the trainings examples, this PR adds a first version of a CLI script which populates a server with a training user/group and some example data. 
Together with this PR, the merge-training job will be rewritten to:
- download the merge CLI
- run the population script against the integration server to create data
- generate a `training_ice.config` file populated with the credentials/object ids
- run the various example scripts using this configuration file

/cc @jburel