BibFormat: more bfe_date parsing/formatting options

* Added parameters to customize the parsing of the date (format,
  source).
  Source format can also be guessed provided that mx.DateTime
  module is installed.

* Special output of year-only dates.

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
BibFormat: new bfe_oai_identifier element

* Display record OAI identifier.

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
BibFormat: /record configurable via CFG_SITE_RECORD

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
BibFormat: improve Dublin Core output

* Added record URL to <dc:identifier> element.

* Added 037$a AND 088$a to <dc:identifier> element.

* Added OAI identifier (CFG_OAI_ID_FIELD) to <dc:identifier> element.

* Added 0247_a to <dc:identifier> element when 0247_2 is "doi".

* Added 260$b to <dc:publisher> element.

* Display corporate author (110__a/710__a) when author is not
  available (100__a/700__a).

* Updated <dc:date> element to fetch data from bfe_date.
  Fall back to record creation date if no value found.

* Removed link to files (8564_u).

* Closes #320

* Closes #1213

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
BibFormat: advertise /doi URL in DC output

* In Dublin Core output (DC + OAI_DC), prefer the CFG_SITE_RECORD/doi/[...]
  url scheme over the CFG_SITE_RECORD/record/[...] one.

* Introduced CFG_BIBUPLOAD_INTERNAL_DOI_PREFIX to differentiate
  between internally managed DOIs, and DOIs assigned/owned by others.

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
BibEdit: prevent deletion of managed DOIs fields

* Check if the fields requested to be deleted contain a managed
  DOI.

* Check if the record requested to be deleted contains a managed
  DOI.

* Introduced CFG_BIBEDIT_INTERNAL_DOI_PROTECTION_LEVEL in order
  to control the behaviour regarding deletion of managed DOIs:
  Ask user confirmation before deleting, forbid deletion or
  simply proceeed. (closes #1445)

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Acked-by: Javier Martin Montull <javier.martin.montull@cern.ch>
BibMerge: prevent loss of DOI when merging records

* Check that no managed DOIs are lost when merging records.

* Check that no duplicate DOIs are created when merging
  records.

* Behaviour regarding deletion of managed DOIs when merging
  can be tuned with CFG_BIBEDIT_INTERNAL_DOI_PROTECTION_LEVEL.
  (closes #1446)

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Acked-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Merge pull request #23 from egabancho/master-oaipmh-doi-update+doi-config-vars

Master oaipmh doi update+doi config vars