Bug 6874: License Text Update

Bug 6874: License Text Update

This updates the license text for
- C4/UploadedFiles.pm
- cataloguing/value_builder/upload.pl
- opac/opac-retrieve-file.pl
to GPL v3 as per the
http://wiki.koha-community.org/wiki/Coding_Guidelines#Licence
text.

TEST PLAN
---------
1) Don't apply this patch as part of 6874.
2) Run the koha qa test tool.
   -- It will FAIL for those three file.
3) Apply this patch
4) Run the koha qa test tool.
   -- License problem is corrected, no FAILs.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>