Bug 3738 Automate login to web-based self-check system

Bug 3738 Automate login to web-based self-check system

Some small, single-branch corporate and special libraries use unattended self-checkout stations, and would like to automate the staff login, so that just going to the sco/sco-main.pl URL would bring the self-check up ready for patron use.  This patch create three sysprefs, AutoSelfCheckAllowed, and AutoSelfCheckID/AutoSelfCheckPass. If the site wants to allow automated login, staff would then need to create the selfcheck user record and enter that login ID and password into the sysprefs.  The kohaclone/opac/sco/sco-main.pl script has been modified to check these sysprefs and pass values (if present and allowed) into the self-check URL.  The URL then bypasses the staff login page and comes up ready for checkout, waiting for the first patron barcode.

Signed-off-by: Galen Charlton <gmcharlt@gmail.com>