Adding KStream sample applications

Add sample for the canonical WordCount
Showing how to track group of products
Showing how to implement interactive queries

Fix #41

Update scst versions
Enhance kstream samples

kstream/kstream-interactive-query/README.adoc

@@ -0,0 +1,46 @@
+== What is this app?
+
+This is an example of a Spring Cloud Stream processor using Kafka Streams support.
+
+The example is based on a contrived use case of tracking products by interactively querying their status.
+The program accepts product ID's and track their counts hitherto by interactively querying the underlying store. \
+This sample uses lambda expressions and thus requires Java 8+.
+
+==== Starting Kafka in a docker container
+
+* Skip steps 1-3 if you already have a non-Docker Kafka environment.
+
+1. Go to the docker directory in this repo and invoke the command `docker-compose up -d`.
+2. Ensure that in the docker directory and then invoke the script `start-kafka-shell.sh`
+3. cd $KAFKA_HOME
+4. Start the console producer: +
+Assuming that you are running kafka on a docker container on mac osx. Change the zookeeper IP address accordingly otherwise. +
+`bin/kafka-console-producer.sh --broker-list 192.168.99.100:9092 --topic products`
+
+=== Running the app:
+
+Go to the root of the repository and do:
+
+`./mvnw clean package`
+
+`java -jar target/kstream-interactive-query-0.0.1-SNAPSHOT.jar --kstream.product.tracker.productIds=123,124,125`
+
+The above command will track products with ID's 123,124 and 125 and print their counts seen so far every 30 seconds.
+
+* By default we use the docker container IP (mac osx specific) in the `application.yml` for Kafka broker and zookeeper.
+Change it in `application.yml` (which requires a rebuild) or pass them as runtime arguments as below.
+
+`spring.cloud.stream.kstream.binder.brokers=<Broker IP Address>` +
+`spring.cloud.stream.kstream.binder.zkNodes=<Zookeeper IP Address>`
+
+Enter the following in the console producer (one line at a time) and watch the output on the console (or IDE) where the application is running.
+
+```
+{"id":"123"}
+{"id":"124"}
+{"id":"125"}
+{"id":"123"}
+{"id":"123"}
+{"id":"123"}
+```
+