Update login page to display broadcast message

What does this MR do?

Update the login page style to display the broadcast message.

Why was this MR needed?

Non-authenticated user can now see the broadcast message from the login page (usually, broadcast message is a general announcement).

Screenshots (if relevant)

Capture_d_écran_2017-05-31_à_00.46.30

Google Chrome

Capture_d_écran_2017-05-31_à_00.47.27

Firefox

Capture_d_écran_2017-05-31_à_00.46.09

Safari

Capture_d_écran_2017-05-31_à_00.45.44

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #13634 (moved)

Edited by username-removed-42381