scirius: implement authentication on all pages

This patch adds a middleware to force authentication to every page.
rules: factorize footer

Using an include allow to have one edit point on all pages (as
login has a different base template).
scirius: implement logout

Add a logout link in top left dropdown menu.
scirius: add reverse proxy capability

Kibana and Elasticsearch are not by default protected by
authentication. To avoid a new layer of authentification, scririus
is now able to reverse proxy connections to Kibana and
Elasticsearch. This makes a cheap SSO solution. If you want to
implement this you will need to setup your Elasticsearch and Kibana
to have them not accessible from outside. Scirius will then be able
to be used as the only gateway.
doc: improve requirements list
scirius: login page redirect to asked page
accounts: new module for user handling

Move authentication function to a new module. This will allows to
keep scirius simple. And it should provide a way to disable it if
needed.
accounts: add user edit and password change
rules: improve drop down menu
scirius: basic user management

It is now possible to create, edit and deactivate users.
accounts: display superuser info
accounts: fix user creation

Use correct form so password is saved.
accounts: only superuser can edit users

Don't allow non superuser to change users accounts.
rules: fix object_list template

div were closed in the wrong part of the if.
accounts: simplify edition

One single page for edition is easier.
accounts: add user deletion
doc: authentication is now by default