bug 8798: (follow-up) pass DB connection params to DBIC schema updater explicitly

bug 8798: (follow-up) pass DB connection params to DBIC schema updater explicitly

This patch changes update_dbix_class_files.pl so that the connection
parameters to the reference database must be passed explicitly via
command-line switches, rather than grabbing them from the current Koha
context.

The purpose of this is to intentionally put up a roadblock to reduce
the chance that a developer (or release manager) accidentally updates
the schema files to include local testing cruft such as temporary
tables.

Usage is now as follows:

[1] Create an empty database
[2] Load the schema creation script into it, e.g.,

mysql -u dbic -pdbic dbic < installer/data/mysql/kohastructure.sql

[3] Run the schema updater:

./misc/devel/update_dbix_class_files.pl --db_user=dbic --db_name=dbic --db_passwd=dbic

Signed-off-by: Galen Charlton <gmc@esilibrary.com>