Bug 15154: Allow correct translation for upload local cover image

Bug 15154: Allow correct translation for upload local cover image

To test:
-Set syspref LocalCoverImages and OPACLocalCoverImages to Allow
-A new tab 'Images' appear in bib record detail on Intranet.
-Notice about the phrase "Please upload one"
-Apply the patch and reload the page.
-New phrase appear "Select the image file to upload" with button Upload
-Update translation files : cd misc/translator; perl translate update es-ES
-You will see in es-ES-staff-prog.po the new entry
"Select the image file to upload. %sUpload%s"
-You can see the result installing the translation
cd misc/translator ; perl translate install es-ES

Signed-off-by: Frederic Demians <f.demians@tamil.fr>
  A native English speaker could confirm that the wording is ok: Please select
  the image file to upload

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>