Bug 20301: Allow translating "View" in manage MARC import

Bug 20301: Allow translating "View" in manage MARC import

When looking at the table showing the staged MARC records, the "View"
text in the Diff-column is not translatable. Make it so.

Test plan:

1) Go to Home -> Tools -> Stage MARC records for import
2) Select eg. t/db_dependent/www/data/marc21record.mrc and upload the file
3) Click on Stage for import
   -> Manage staged records
   -> Import this batch into the catalog
4) Wait for zebra to reindex, or trigger it yourself by
   running rebuild_zebra.pl -a -b -r
5) Go to Home -> Tools -> Stage MARC records for import
6) Select the same file as in part 2 and upload the file
7) Change the Record matching rule to ISBN (020$a)
8) Click on Stage for import
   -> Manage staged records
9) In the table below, there should now be a line showing
   the staged MARC record matches biblio
10) Note the "View"-text in the "Diff"-column
11) Apply patch
12) Install a language, view the same batch in the
    Manage staged MARC records -page in that language
13) The "View" should show up correctly, and if the
    msgid "View" was translated in the xx-YY-staff-prog.po,
    should show up in the correct language

Signed-off-by: Pasi Kallinen <pasi.kallinen@joensuu.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>