MODE-2340: Can not log out from Repository Explorer application

This PR implements logout procedure:
- remove credentials; 
- resets view to the entry page with repositories;
- invalidates existing HTTP session
So if someone logs out, they will always be taken to the list of repositories?

Would it make more sense to try to stay at the current page as an anonymous user if that location is readable to anonymous users, and if not readable then redirecting to the repositories page?