Calculate scale of matched characters

Also adds filtering on inconsistent scales within chars. Catches some
things like spurious Xs and +s in various symbols.
Capture remaining characters: R, F, Y, K, J

Requires machinery for changing scale of a sigil since these are at
different scales within P1318-005a.pdf.
Slightly increase tolerance

This matches the 3 at the start of the date at the bottom left of
P1318-005a.pdf.
Operate on all pages

(Currently does nothing but mark /s and Vs in the CC logos, probably
since the page orientation is hardcoded and doesn't work on the first
page, which is portrait instead of landscape).