measureBasedView: auto fit facsimile to window on window resize

[bwbohl]

having opened all participants from an annotation, the opened source windows might be very small; maximize/restore on single windows will help inspect then content; adjusting page size of "virtual staves" requires adjusting pageSize of two images thus only solution is to "fit facsimile" from source view viewMenu; this will adjust size of both facsimile areas. This should be automatically triggered on window maximize/restore.