Governance - add createdAt and updatedAt attr in the results of the searcn endpoint

To avoid make an extra calls to the GovernanceAPI from the FrontEnd, the following attributes are needed in the results of the search endpoint:

• createdAt
• updatedAt

Current response (one item):

{
        "id": "9576b1e6-c451-4f0e-b595-5682bc9c84fe",
        "type": "DcatDataset",
        "name": "New E-Redes files",
        "description": "New E-Redes files",
        "summary": "New E-Redes files",
        "terms": [],
        "domains": []
}

/cc @anacosta, @hugoloba