KitInformationConfigWidget: Make id of KitInformation accessible

Make the id of the kitinformation the config widget is configuring
accessible from the widget.

Change-Id: I15af2cfc18ab2ba012d43c3c6b71ee0011f994ad
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>