- add new links dropdown to top navigation in template base.html
- add new settings GVA_LINK_WEBMAIL, GVA_LINK_PHPMYADMIN and
GVA_LINK_PHPPGADMIN to gnuviechadmin.settings.base
- implement gnuviechadmin.context_processors.navigation to add links to
request context of non-AJAX requests
- add generated documentation for gnuviechadmin.context_processors
- add changelog entry