Improve installer creation script

SdkUpdateRepository is not mandatory in configuration files so
the script should not fail if the section is not present in
configuration files.

Also do not limit the component count for online installers. Allow the
online installers to include more than the plain root component.

Change-Id: I8c578dc17819459d6ba1cbb14d888e7787c08954
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>
Reviewed-by: Antti Kokko <antti.kokko@digia.com>