Setup Phabricator import

This is an EE port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27877

The conflicts were:

  • config/sidekiq_queues.yml -> Add the new queue on top of the EE specific ones instead of the bottom of the file
  • lib/gitlab/github_import/parallel_importer.rb -> The prepend and the new include were conflicting, moved the prepend to the bottom of the file
  • locale/gitlab.pot -> Regenerated