WebSearch: discussions compatibility fix

* Reverts counter of discussions for legacy app.  (closes #1422)
WebStyle: non strict handling of last slash in url
WebSession: fix typo in setUid

* Fixes become user feature.  (closes #1424)

Reported-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
inveniocfg: --create-secret-key new line addition

* Appends CFG_SECRET_KEY to invenio-local.conf with new-line.
  (closes #1406)
WebSearch: force integer type of recid
WebAccess: addition of redirections to legacy app

* Fixes problems with patially ported admin interface by adding
  redirections to legacy application.  (fixes #1425)

* TODO reimplementation of resetarea, manageaccounts, delegate_startarea
  and managerobotlogin.

* PEP8 improvements.

Reported-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
importutils: initial release

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
DocExtract: model file move
BibIndex: model *19* addition
WebStyle: autodiscovery of models on app creation
jinja2utils: LangExtension initial commit
WebMessage: fix link on /yourmessages
WebStyle: fix for remote host getter
WebSession: authentication with email address

* Enables local authentication by email.  (addresses #1338)

* TODO migrate LDAP, OAuth and Single Sign On plugins.
WebStyle: database creation in app factory

* Addresses problems of model imports before application context
  is created by wrapping fixtures in closure passed to new
  InvenioFixture class.

* Adapts all relevant test cases.
SQLAlchemy: support for version 0.8.0

* Replaces incompatible mutable attribute by MutableDict.
  (closes #1409)

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