Add logout link

[arianvp]

There's a special callback for the oauth integration that logs the user out. we should at a link to it. (I'm not sure if it's a POST handler or not)

[duijf]

Not opposed to add some custom links. However, I'd like to keep pxl generic. We should allow this in the config.

[tomwassenberg]

Maybe it would be possible to (also/instead) add this option in Koala? Something like a "connected apps" overview.