fixes #4174 - fixed locale distribution and jenkins rake task

Two issues from RC1 resolved plus i18n support is fully working now. Although
i18n plugin support does not support javascript and model localization, we do
not use these in Discovery.

Also, there is a PR coming to Foreman with minor changes in the Makefile script
to better support plugin extraction.

Packagers note: Please do this command during package build to prepare MO
files:

    make -C locale all-mo

That should create locale/*/LC_MESSAGES/discovery.mo files.