BibEdit: change cache folder

* Changes from tmp-shared to tmp-shared/bibedit-cache

Conflicts:

	Makefile.am
BibEdit: avoid sync request to see if record has pdf
BibEdit: save changes periodically

* Saves changes to server periodically (frequency can be
  configured) in bulk and asynchronously to avoid slowing
  down client.
BibEdit: add direct link to dx.doi.org

* New icon to search for DOI on the dx.doi.org page,
  if the DOI is found it opens the page on new tab

* Fixes the border of textareas (right border was invisible)
BibEdit: sort HoldingPen changes alphabetically

* Orders the subfields from the holding pen entry
  alphabetically before making the comparison with the
  current record
BibEdit: add version to bibedit css name

* Prevents browser from caching the css file if it has
  changed on disk
BibEdit: use perform_request_search on search

* search box now uses perform_request_search instead of
  search_pattern
BibEdit: refactoring and fixes

* Refactoring of functions related to editable area change

* Sets max characters on fields/subfields

* Avoids double bind of editable area. Was causing troubles.

* Fix bug in field tag modification undo

* Fix switch to write mode

* Fix merge with template. Record was not being ordered after
  merging with template, so operations on the recstruct where
  not being done correctly

* Change in css to always display scrollbar in webkit-based
  browsers.
BibEdit: fix perform_doi_search function

* Adds 'User-Agent' to the headers send within the
  perform_doi_search function

* Adds CFG_DOI_USER_AGENT to the bibedit_config file

* Adds CookieJar to store cookies on the pages redirected
  from the dx.doi.org

* Adds unittests for the perform_doi_search function

Reviewed-by: Javier Martin Montull <jmartinm@cern.ch>