UnknownPage -> multiple extra pages
The following discussion from !1217 (merged) should be addressed:
Is it worth trying to work into this "single-unknown => multiple extra pages (ie several questions) "
Can we easily modify unknownToExtraPages to allow mapping page "Unknown123" onto say questions 1, 3, 6?
Note: thread discusses that this is a less-atomic operation (?)
Say Q3 is not scanned, but Q1 and Q6 succeed... Need to decide what should happen.