Branchoverdues circ report reworking.

Branchoverdues circ report reworking.

branchoverdues.pl
~ Removed unused variables.
~ Use elsif where applicable.
~ Added many FIXMEs.
~ Added help description.
~ Changed link to more accurate description.
~ REFACTORED branchoverdues-specific function in C4 for obvious consolidation.

This report is still of questionable value, since it's dataset has such strange
hardcoded limitations.  It is not clear that "FU" type fines and notifys=0 are
reliable or useful indicators to query on, in hardcoded form.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>