Bug 19522: Label creator: edit batch: make "Export label" translatable

Test plan:
1. install the fr_FR locale
2. go to /cgi-bin/koha/labels/label-manage.pl?label_element=batch
3. create a batch if there is none
4. edit that batch
5. Switch the language to French if you haven't done it yet
6. click on "Exporter le lot entier"
7. then you should see "Export labels"
8. apply this patch
9. install the language
10. replay steps 2 to 6
11. then you should see "Exporter des étiquettes"

Signed-off-by: Simon Pouchol <simon.pouchol@biblibre.com>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

koha-tmpl/intranet-tmpl/prog/en/modules/labels/label-edit-batch.tt

@@ -98,10 +98,10 @@
                         alert(_("Please select at least one label to export."));
                         return;     // no batch selected
                     }
-                    return GB_showCenter('Export labels', "/cgi-bin/koha/labels/label-print.pl?batch_id=[% batch_id %]&" + getstr, 400, 800);
+                    return GB_showCenter(_("Export labels"), "/cgi-bin/koha/labels/label-print.pl?batch_id=[% batch_id %]&" + getstr, 400, 800);
                 }
                 else if (mode == 'batch') {
-                    return GB_showCenter('Export labels', "/cgi-bin/koha/labels/label-print.pl?batch_id=[% batch_id %]", 400, 800);
+                    return GB_showCenter(_("Export labels"), "/cgi-bin/koha/labels/label-print.pl?batch_id=[% batch_id %]", 400, 800);
                 }
                 else {
                     // some pass-thru error trapping just in case...