Send pairing notification from the pairing details view

[hopffgam]

When we change a pairing manually we sometimes would like to (re)send a pairing notification to the players. In order to send that message we have to exit the pairing details view (which itself is accessible via the normal pairings page) and go to the tournament admin > player pairings.

It would be nice to be able to send the pairing notification directly from the pairing details screen. However, we have to ensure that this message goes to the correct players, e.g. when a player on the pairing was changed but it has not been saved yet.