Bug 20115: Make the prefs sortable

Bug 20115: Make the prefs sortable

If we depend on the order, we should make it sortable.

I let the customization to someone else (we would need an icon to tell
the user it's sortable).

Something does not work here:
If fr-FR and fr-CA is installed, but only 1 is ticked, it will be
considered as last. I do not think it's a blocker as it does not make
really make sense to have it installed but not used (the interface is
also weird, there is a dropdown list with only 1 entry)

Signed-off-by: Jesse Maseto <jesse@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>