Bug 8633 Manage OPAC alternate templates

Bug 8633 Manage OPAC alternate templates

Modify /misc/translator/translate script in order to manage properly alternate
OPAC templates.

To test it with new 'ccsr' template:

- Create the .po file:

  ./translate create fr-FR

  Result: existing .po files are not modified. A new fr-FR-opac-ccsr.po file is
  available.

- Install all templates :

  ./translate install fr-FR

  Result: A new koha-tmpl/opac-tmpl/ccsr/fr-FR directory contains translated
  templates.

- Update .po files:

  ./translate update fr-FR

  Result: fr-FR .po files are update, include fr-FR-opac-ccsr.po

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>