Bug 27695: Fix style of messages on Elasticsearch configuration page

Bug 27695: Fix style of messages on Elasticsearch configuration page

This patch makes minor modifications to SCSS and HTML to make messages
on the Elasticsearch configuration page more consistent with other
interfaces.

To test you should have Elasticsearch selected as your search engine.

- Apply the patch and rebuild the staff interface CSS
  (https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client)
- Go to Administration -> Search engine configuration (Elasticsearch)
- You should see a full-width "note" style message under the page
  heading, "Warning: Any changes..."
- Click the "Reset mappings" button at the bottom of the page. The
  confirmation alert you see should appear above the note-style message.
- I'm not sure how to trigger an "error" type message on this page, but
  you can test the updated style by going to Administration ->
  Currencies and submit a new currency with the same name and symbol as
  one which already exists.

Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>