Improve GUI navigation

[VauteerU]

To make it easier to check many payment details it would be good to be able to open the payment page in a new tab so that the scrolling position in the payment list is not lost for the next check.
Alternatively, it would also help if the payment list remembers the scrolling position and the configuration of the rows shown (default 10) when coming back from a payment detailed page via the browser's back button. However, that is probably difficult since it is handled on the client's side.