Stay on same page after logout 

If the anonymous user does not have the permissions, they are
redirected to the login in the next step.

Closes COUCHDB-2435

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Only exception here are actions that don't open a new page, e.g. in a database that is only accessible as admin, logout and click `changes`. You will get a spinning wheel of death and an error notification. So far no general solution came to my mind, open for suggestions!