Bug 12169: Use pid file in sipserver shutdown

Bug 12169: Use pid file in sipserver shutdown

Change sample SIPConfig to request server writes a pid file

Use this pid in shutdown rather than the current open to error
method.

Have also added to the Config parameters to ensure that the sipserver
runs as the correct user and sets its own session id. These are always
useful but makes it easier for users to run up the sipserver as root at
boot time similarly to apache, mysql etc

Added to the sample config where to locate other server parameter
documentation.

Removed from the sample config the unedifying, unwanted and
purely historical http example

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>