As an admin I want to choose the lmcc interface language in the login & registration page

This is a follow-up story for #138 (closed)

Requirements:

• When I go to the login page, I want to be able to select the interface language from a dropdown menu in the application footer.
• If the login succeeds, the application should continue using the language selected during login.
• Otherwise, the application language should remain unchanged, but the login page should continue in the language selected by the user.

Implementation issue: an unauthenticated user should not be able to change the application settings.