Text to go in the release notes:
To ease multi-tenant sites maintenance, several handy scripts were introduced. For handling SIP servers, 3 scripts were introduced: koha-start-sip, koha-stop-sip and koha-enable-sip.
This patch introduces a new script, koha-sip, that unifies those actions regarding SIP servers on a per instance base, through the use of option switches.
18.11 Note: The introduction of this script does NOT remove the koha-*-sip versions at this time and the scripts can be used interchangeably until one upgrades to 19.05 where the koha-*-sip versions are officially removed.