Add S2I support for the iot-demo

[ppatierno]

As proposed by @mbogoevici it could be useful having the S2I support in the iot-demo in order to build the device-app and stream-app Docker images in the OpenShift cluster directly from the GitHub repo.

[gunnarmorling]

Yes, I think that'd make sense. We could also use S2I for creating Strimzi images of Kafka Connect with the Debezium connector used in the lab.