Bug 28159: URI-encode existing values put into query string for z39.50 authority...

Bug 28159: URI-encode existing values put into query string for z39.50 authority search

When you trigger a z39.50 search from an existing authority record,
Koha prefills the search form with the value in the record. But because
that value passes through a URL, if it isn't URI-encoded characters like
& or ; will cut off the value.

Test plan:
1) Authorities - New authority - Corporate Name
2) Tab 1, click "HEADING-CORPORATE NAME" to expand subfields
3) Subfield a, type foo & bar ; baz
4) Click Z39.50/SRU search
5) Ensure the whole string appears in the Author (corporate) field in
   the popup

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>