Now compiled locale files (.mo) are generated on the server side.
This cleans up the git tree and make translation contributions much
easier to merge.

Please note that you will need to generate those files after each pull,
so remember to execute install_re2o.sh.

Now `manage.py gen_contrib` generates a contributors.py matching the
already existing format. It normalizes names to make the list more
enjoyable.

Before using this to seriously generate contributors.py we need to
figure out a way to add pseudo names, or tell everyone to change their
name on GitLab.

Rather than going online, use fonts-font-awesome debian package. Also
icons were updated to font-awesome 4.7.0 (in debian 9).

* Rather than using href="\\host/about/" in page footer, use
  href="protocol://host/about/"

* The old footer uses hacks to be staticly on the bottom. To make it
  much simpler one solution is to turn it white and use official
  Bootstrap code. This leads to less CSS to maintain and better
  cross-browser compatibility.

* On re2o about page (/about/) there is some typos such as :
  * assocations > associations
  * legitlab > le gitlab

* Use Bootstrap navbar-static-top rather than custom CSS.
  The result is the same, so we should be better using directly
  Bootstrap CSS.

An attacker knowing the salt but not the hash could try timming-attacks
to guess a password hash and then try to find it from the hash.
Although not a high risk, there is no good reason not to use a
constant-time comparison, hence this commit.