Add universal ID for each submission

[nhamilakis]

Feature requested for the zerospeeech challenge 2.0.

A comparative of models that have competed in different issues of the challenge (same benchmarks) is requested.
To achieve this, each model submitted to a benchmark needs to have a unique ID.

• The MODEL_ID's need to be short (so as to be referencable in plots/texts/papers etc...)
• The MODEL_ID's need to be able to span multiple submissions (as the same model could participate in multiple challenges/benchmarks)
• There needs to be an API section that allows to preview info & results by model /models route.