New endpoint to clone a dataset

Refs https://redmine.teklia.com/issues/3653

A new endpoint named CloneDataset must be available to corpus contributors, and allow them to clone the specified dataset (through its ID).

All atributes are copied:

• name is prefixed with "Clone of "
• description remains unchanged
• sets remain unchanged
• all elements associates to the source are also associate in the clone, using the same set name

The endpoint must return the ID of the cloned dataset.

The different operations are made during the time of the request (no async)