bug 2503: refactoring and bugfixing on create_koc_db.pl

bug 2503: refactoring and bugfixing on create_koc_db.pl

This is the script that generates the patron and holdings database for the offline circ module. I
touched up a few parts of it:

* fixed the database syntax to squash a bug or two
* extracted some methods for readability and reuse
* added some documentation
* added a --file and --force command line argument
* made it die if DBD::SQLite is not present. That module is required for this feature.

Here's an example crontab line that will generate the borrowers.db file each midnight.

0 0 * * * create_koc_db.pl --file /tmp/borrowers.db

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