Bug 14252: (followup) fix lang chooser for sublanguages

Bug 14252: (followup) fix lang chooser for sublanguages

This quick fix disables sublanguages dropdown,
show all sublanguages on same level.

To test:
1) Apply both patches
2) Translate to have sublanguages (en-NZ, de-DE, de-CH)
3) Go to opac, confirm you can select any lang/sublang
4) Check on movil device

4th version.
Removed rfc4646 subtag on sublanguages, think it's cleaner.
Currently on master all translated languages/regions have
valid description ('en' at least)
Added language sort using rfc4646 subtag

Signed-off-by: Indranil Das Gupta <indradg@gmail.com>
Followup fixes the issue with lang group dropdowns. Works well
across standard desktop as well as mobile device with small screens
(checked on 4.3" / 4.7" / 5")

Works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>