Given that it changes the "capture" button from
single image acquisition to a long running scan,
I think it's less confusing if the "scan capture" setting
is not remembered across page refreshes.
Saving default to local storage has a problem:
if you have ticked "scan", the section is not
visible by default so it's easy to start a scan
by accident. I've now forced it to be open if
the scanCapture checkbox is true.
It doesn't make sense to allow fewer than 1 image in any dimension
of a scan. Currently, supplying 0 gives a division by zero error.
I've added min="1" to each control.
