IAbookreader ZOOM functionality parsing URL fails on File Names (IIIF IDs) that contain the word FULL

# What?

A hard to hit issue.

If your PDF (or image) contains the word "full" in its name, the OSD overlay won't be able to split the URL correctly ending with a broken Overlay.

Fix is to use a stricter IIIF aware parsing mechanism (a maybe even deal with non IIIF images too?)

Regular expressions and splitting. Maybe even a IIIF URL parser function helper