testutils: regression tests fix

* Addresses issue with broken 'xm' output format.

* Improves landing page compatibility with regression tests.

* Adds `unittest2.TestCase` as base class for `InvenioTestCase`.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
WebComment: prepare attachement location fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
BibFormat: regression tests fix

* Adresses problem with incorrect output format handling in search
  results.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
WebSession: customizable settings widgets

 * Fixes saving settings widgets.

 * Fixes closing and opening widgets.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
WebSession: settings widget closing fix

* Adds lazy loading of user settings widgets.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
BibFormat: fix preview record using tpl

* Adresses problem with formating record using Jinja2 template from
  MARCXML without record id.

Signed-off-by: Raquel Jimenez Encinar <raquel.jimenez.encinar@cern.ch>
Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
installation: release control fix

* Informs super admins if newer version of Invenio is released.

* Adds new manager command `check-for-software-updates`.

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
dbquery: regression tests fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
mailutils: config email backend preference

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
inveniocfg: stop logging capture fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
dateutils: move of dateutil version detection

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
WebSearch: regression tests fix

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>