engine: docs other languages

- If you try to load a manual document in a locale that
  doesn't exist, you will get a 404 instead of a warning
  message that the language is not available.
- Fixed issue in the path of the link that would forward
  you to the english documentation.
- Fixed issue in the cookie path that would store if you
  had been shown the warning message yet.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1083528

Change-Id: Iaa26e9a95eff3aa117517ec53d3d97c8ac5ba703
Signed-off-by: Alexander Wels <awels@redhat.com>