Nuxeo Drive: GUI to enter Nuxeo URL / Username / Password to fetch token

The first time drive is started, a QT GUI prompt should be displayed to bind it to a server using the user credentials.

Subsequent calls will reuse the token fetched the first time hence will not require many user intervention.

This would be equivalent to the existing ndrive bind-server username url --password password commandline operation but using a GUI to make it more user friendly.