Return response as csv

[cristianpb]

For route '/search', when header has "Accept: application/csv" the response will be a csv with the matching identities.

The csv includes the following properties:

  'score', 'source', 'id',
  'name', 'firstName', 'lastName',
  'sex', 'birthDate', 'birthCity',
  'cityCode', 'departmentCode', 'country',
  'countryCode', 'latitude', 'longitude',
  'deathDate', 'certificateId', 'age',
  'deathCity', 'cityCode', 'departmentCode',
  'country', 'countryCode', 'latitude', 'longitude'

I think they should be renamed using the modifications on #62