admin/site language switch interaction

In adminmode there are two language switches: The global one in the topbar (site specific) and the one in the toolbar.

These don't interact nicely. When administrating this may be unavoidable (e.g. different domains per language) but if the site works with/supports i18n pattern paths, the two selectors should be able to work in sync. This probably means not depending on an admin_language cookie.
