Bug 14030 - Added tests for duplicates.

Bug 14030 - Added tests for duplicates.

It seems that the id's are not really used, but rather
the subtags, types, and language related fields.

These tests check for duplicates.

TEST PLAN
---------
1) Apply both patches
2) prove -v t/db_dependent/Languages.t
   -- may fail if you have duplicates.
3) ./installer/data/mysql/updatedatabase.pl
   -- this will trigger the atomicupdate, which because of
      this tweak, will correct duplicates.
4) prove -v t/db_dependent/Languages.t
   -- should succeed.
5) Run the updatedatabase.pl script multiple times.
6) prove -v t/db_dependent/Languages.t
   -- should still succeed.
7) koha qa test tools.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
No koha-qa errors, test run successfully, no more duplicates

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Fixed German description.

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