Refactor formatting code to properly handle chronology

Refactor formatting code to properly handle chronology
information stored in the enumeration fields (well, I think it's
handling it properly; it hasn't been tested yet for that case).

Also refactored basic next/prediction code to handle the same
situation. Basically this is all minor stuff that needs to be
done, but allows me to avoid working on actually taking a stab at
predicting the date of the next issue, but that's pretty much all
that's left to do for this iteration of the code.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@11359 dcc99617-32d9-48b4-a31d-7c20da2025e4