output JSON Keys should be customizables

[roigcarlo]

Problem:
Most keys in json output file are hardcoded.
It is interesting to have the h ability to change them.

Example:

"processes": {
    "default_key_process": [{ }],
    "custom_key_1_process" : [{ }],
    "custom_key_N_process" : [{ }]
}

[rubenzorrilla]

Adding as a reminder that the main key processes, as well as output_processes, must remain hardcoded as this is what we parse in the AnalysisStage.