bug 2884: followup patch

bug 2884: followup patch

[1] Restore behavior of the input field for the library
    code; when adding a new library, it should be a
    a text box; when editing an existing library,
    should be a hidden input.
[2] When user attempts to add a new library with the same
    code as that of an existing library, populate the form
    with what the user entered for the new library, not the
    values from the existing library.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>
Signed-off-by: Henri-Damien LAURENT <henridamien.laurent@biblibre.com>