Fix for @vskh reported issue with previous PR.

Just using a different, not-used classname.
Update
use our own get_language_from_request instead of Django's

django's get_language_from_request has a global "_accepted" cache which,
for some reason not quite clear to me, always contains en_US. This interferes
with our allowed frontend languages: translation.get_language_from_request
returns "en" even if it's not an available language
Merge pull request #1717 from mkoistinen/develop

Fix for @vskh reported issue with previous PR.
Merge pull request #1719 from piquadrat/feature/frontend-lang-fix

use our own get_language_from_request instead of Django's
Added Evgeny Demchenko to AUTHORS
Merge pull request #1721 from littlepea/develop

Added Evgeny Demchenko to AUTHORS
fixes #1715 and no i18n tests
missed something
Merge pull request #1722 from digi604/fix-1715

fixes #1715 and no i18n tests
made the check_copy_relations check a bit smarter by taking superclasses in account

fixes #1723
clears url caches
Merge branch 'fix-1715' into develop
fixes testsuite
Merge pull request #1724 from piquadrat/feature/fix-1723

made the check_copy_relations check a bit smarter by taking superclasses in account
Readd viewsitelink CSS class to page change_form template

This is needed for finer control over the link's styling.
Merge pull request #1726 from jalaziz/fix-viewsitelink

Re-add viewsitelink CSS class to page change_form template
2.4.1 - authors, changelog and version bump
Fix wrong PROJECT_PATH in the tutorial