feat: multiple masking config

[P0labrD]

Close https://github.com/CGI-FR/PIMO/issues/23.

Note: this is a draft request; the question of the seed can be discussed:

• keep the coherence between files: if both files has the same seeding, the global config should have the same seeding
• generate a new seeding: global seed = seed1 + seed2 ( or another operation)

Less important: the version (in my understanding, the version field is not used in the pipeline, it's just useful for the user to keep track of the version of his files)

[P0labrD]

PR https://github.com/CGI-FR/PIMO/pull/92 might help for the problem of seeding. It needs to be discussed.