Factorize scenario creation

[n-peugnet]

Based on #63, so should be merged after ideally.

This adds two important features:

Ability to directly pass json to the cli

It is now possible to pass a scenario two different ways:

• with a scenario file with --scenario option as before
• with a scenario json string --content option (yes the name is not reaaly good but I didn't find a better one).

With this feature it is now possible to not have the scenario file on all machines with MPI. It will also allow to directly pass a Scenario object from Java without creating a file (when we will add the ScenarioBuilder).

Completely abstract Scenario creation for implems

with this feature implems do not have to parse the scenario themselves so it is a good improvement for the ease of creating a new adapter (part of #51). Also there isn't any null check anymore as the Scenario Object is now always present but it can be empty of events.

[n-peugnet]

After some thinking I want to rename:

• the class Scenario into Config
• the cli option -s, --scenario into -c, --config
• the cli option -c, --content into -j, --json