allow crossed bells

[annag42]

Allow an option for Wheatley to recognise either bell rung in a handbell pair held by one ringingroom account, when running in handbell mode, in order to allow more smoothly for the handbell-ringing convention of the ringer whose bells are crossed (but otherwise corrected placed) just correcting the order of their own bells on the next row. This seems like it would make things easier on the human ringers in a room with Wheatley, and help Wheatley seem more polite, by fitting in with existing handbell-ringing conventions in a more unobtrusive way.