[MetaData] Add support of cascading creation in POST method of resource /data/{type}

[arcadmlafon]

For time to time it may be necessary to create a relative data along with the main data. For instance if a Client object is create, then we may need to create its "owner" User at the same time, so a call like:

POST: /data/client
{ "name": "ACME Corporation", "owner.firstName": "E.", "owner.lastName": "Wile" }

should allow to create in one unique call the client and the owner of this one.