Merge pull request #18 from openfun/issue753_allow_university_group

#753 allow university groups
#723 add view for grades download in fun_instructor app
##723-2.1 catch exception when a file is not found, return 404
Merge pull request #20 from openfun/issue723_grades_download

Issue #723 grades download
Translate "Official" in forum

Fixes issue #868.
Merge pull request #24 from openfun/regis/translate-official

#868 Translate "Official" in forum
Slightly improve universities fr translation file
Use lazy translations in forms
Use lazy translation in models

Fixes #898.
Merge pull request #25 from openfun/regis/translate-admin
Add makemessages_fun translation commands

Added a makemessages_fun management command to collect translations for
fun-apps and the fun theme. Go to edxapp and run:

    ./manage.py lms makemessages_fun --settings=fun.lms_dev -l fr all

This should update the locale/fr/LC_MESSAGES/django.po file of all
fun-apps and the fun theme by:

    - adding new, required translations
    - keeping translations that override edx translations
    - removing obsolete translations

Also, update the various django.po files with this script.

Previously, fun theme was not translated at all, as it was all in
French. Now that we handle theme translations (via makemessages_fun), we
are able to localize the theme.

Note that translations are no longer collected in fun-apps/locale/, but
instead they are spread across the various applications, including
fun-apps/fun. Any application can thus override the edx translations.
Move fun translations from locale/ to fun/locale/
Get rid of obsolete v1/ translation folder
Remove useless django.mo_ file
Move theme translations to the theme itself

It is possible to fetch the theme translations at runtime via the
fun-config common settings file.