Allow the pasting of a text clipboard content to the URL navigator by pressing the middle mouse button. Although this is quite a hidden feature, I think it makes happy a lot of people who just want to paste a URL available as text to the URL navigator without switching from the breadcrump view to the traditional view.

Very nice "side effect": the URL navigator is now completely flicker free when changing URLs because of using the whole available width :-)
TODO: I'm not 100 % sure whether checking the middle mousebutton by 'if (event->button() == Qt::MidButton) { ... }' is the right approach (maybe there is a more generic way to check the 'paste button').