Utils: adds DOI json data fetching

* Adds JSON data response for a given DOI.

* Adds etree to dictionary translation on
  processor utils.

* Corrects get_marcxml_for_doi() misuse of
  plain text params in the url.

* Needs the user's email as a configuration
  variable.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Deposit: adds holding pen to deposit

* This task adds the deposition to the
  Holding Pen so it gets approved or
  rejected by an administrator.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Deposit: adds json api to fetch doi from crossref

* This searches the DOI on crossref and returns
  the result as JSON format, also handles if the
  DOI isn't found or it's malformed.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Javier Martin Montull <javier.martin.montull@cern.ch>