Model saving rework

[mbrunel]

Description

Implementation of namespacing

Related Issue

The idea is to identify models between users without having the handling uuid.

Type of change

This change affects the server.

How Has This Been Tested?

Not finished yet.

TODO

• [x] creating on folder by user and saving models inside them when necessary (may need rework already as I'm not sure the way I do it is pertinent)
• [x] limiting uuids use to model sealing (necessart for security reasons), with the format model_name#uuid
• [x] Handling of access rights between normal BlindAI and public / private cloud at query time.
• [x] Limiting number of models per users of Cloud (loaded and sealed)
• [x] Storing models metadata in a separate file to avoid looking at all of them each time

[mbrunel]

It should now be ok for testing, I don't think it's really robust, and it definitively needs some refactoring but I think the key points of the features are fonctional.