Add strict mode into SDK/installer packaging scripts

By default the strict mode is enabled. If any archive, template or
metadata file is missing the script will stop executing. The strict
mode can be disabled e.g. for testing purposes.

Change-Id: Ibf96c93cb68488e34e3017b2f3f2034e1a49ee57
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Simo Fält <simo.falt@digia.com>