global: language value always in link URLs

* Always sets the ln value when creating the URLs to keep the
  user language setting consistent when following those URLs.
  Fixes some URLs in websearch_templates.py and webdoc.py.

Signed-off-by: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>