Fix 404 on vendored images in production

Fixes what was not really fixed by cd3adb402e3a.
Improve creation of user on shibboleth login and more tests

Just reorganized a bit the way it is done, but it still has the same results.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	app/controllers/shibboleth_controller.rb
	lib/mconf/shibboleth.rb
More focus on the federated authentication on /login

As already done in the frontpage.