Create a Nuxeo Avro Schema Store service

When using avro the interesting encoding format is Single object encoding which consist of a schema fingerprint and the avro binary message. This format (AvroMessage) will be used to encode Nuxeo stream record by default.

Avro comes with a SchemaStore interface that need to be implement so we can decode/encode Avro message.

The Nuxeo service should be able to register Avro schemas and provides the access by fingerprint.

A first implementation can rely on contribution, a better implementation could use the KeyValue store which is shared among Nuxeo nodes even if they are not all up to date.

If we want to have interoperability we also need to expose the Schema store with REST, so any third part can read/write our record.