Bug 20135: Prevent staff client language choose pop-up from appearing off-screen

Bug 20135: Prevent staff client language choose pop-up from appearing off-screen

This patch fixes a bug which was introduced by Bug 19851 ("Improve
responsive layout handling of staff client menu bar."). The changes in
that patch did not take into account the effects it would have on the
language menus in the footer.

This patch adds some additional classes to some menus and adds some CSS
for those classes so that menus are correctly aligned left or right
based on their position on the screen.

To test, apply the patch and clear your cache if necessary. You should
have multiple translations installed and enabled, at least one of which
should have more than one "sub-language" (e.g. en-GB and en-US).

In the staff client, test the appearance of various drop-down menus with
the browser width above and below 800 pixels wide:

- Search and More menus in the header
- User/Library menu in the header
- Language selection in the footer
- Language selection in the header

In all cases, menus should look correct and should not be aligned in
such a way that they disappear off the left or right sides of the
screen.

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>