Bug 18644: Translatability: Get rid of pure template directives in translation for...

Bug 18644: Translatability: Get rid of pure template directives in translation for memberentrygen.tt

Translation for memberentrygen.tt exposes a lot of template directives
like the following:
[% UNLESS opduplicate %][% othernames | html %][% END %]
Translators should not be confronted with such code internals.

To test:
- Review code changes
- Verify that creating / editing patrons works as before
- Bonus test: Create a "language" aa-AA (perl translate create aa-AA
  from folder misc/translator, verify that lines like mentioned above
  do no longer appear in aa-AA-staff-prog.po

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