Login: also allow shift-return to trigger login-button

Hello,

just a tiny issue: currently, only return/enter will trigger the login-button, not shift-return.

If one has a password with an uppercase letter at the end, the login-button will not trigger, if the shift-key has not been released (accidently).

This is not a problem under other applications. Shift-return works at almost all dialogs as a trigger for an accept-button.

Best regards, Uwe