multimedia: initial release of Image API

* Introduces image API with `resize`, `crop`, `rotate`, `format` and `quality`
  functionality.

* Adds image cache object via redis.

* Adds API testsuite.

Signed-off-by: Harris Tzovanakis <drjova@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
multimedia: IIIF Image API addition

* Implements the IIIF Image API.

* NOTE For more info please read <http://iiif.io/api/image/2.0/>

Signed-off-by: Harris Tzovanakis <drjova@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
multimedia: Image API documentation update

Signed-off-by: Harris Tzovanakis <me@drjova.com>
formatter: better logging in xslt engine

* Uses `current_app.logger.error` or `current_app.logger.exception`
  instead of `sys.stderr`.  (closes #2049)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
formatter: format record extra context fix

* Fixes issue where certain format_record() method would not accept the
  extra_context keyword argument.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
formatter: xm hidden tags fix

* Fixes issue where hidden tags was not filtered out in xm format due
  to that user info was not passed to the format_record function.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
menu: admin menu visibility fix

* Fixes admin menu to only be visible for admin users.

* Changes admin menu order to 10, to ensure it is the right
  most menu item.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
communities: hbpro format database fix

* Fixes problem in post database creation listener.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
deposit: refactoring fix

* Fixes refactoring issue introduced in
  6e60101a0c9dc7f2350d32872d418446a23cac0c.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
oauthclient: documentation update

* Adds overview documentation and includes it Sphinx docs.

* Fixes minor issue with GitHub/ORCID contrib modules.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>