Streamsx-kafka

This release is a bugfix release that contains following fixes:
* 84 - Add a KafkaTransactionSample to the samples folder
* 83 - Producer behavior when control topic cannot be auto-created? (avoid NullPointerException)
* 82 - Transactional consistent region policy may commit duplicate transactions

Known issues
- When Kafka's group management is enabled (KafkaConsumer not in consistent region and **startPosition** parameter unset or `Default`), the KafkaConsumer can silently stop consuming messages when committing Kafka offsets fails. 98. As a **workaround**, the consumer property `enable.auto.commit=true` can be used in a property file or app Option.

**This release fixes following issues:**

* 75 - KafkaConsumer: InterruptedException not handled properly
* 79 - Consumer commits same offset multiple times
* SPL Documentation: 77, 78, 80

Restrictions
* The `Transactional` value for the **consistentRegionPolicy** parameter requires that a control topic with name `__streams_control_topic` exists in the Kafka broker to store committed transaction sequence numbers. In order to ensure *exactly once* delivery semantics, this topic must be created with **only one partition**. If the broker is configured for automatic topic creation, the topic should be created manually to avoid that it is created automatically with multiple partitions as configured by broker property `num.partitions`.
See also issue 82.
Known issues
- When Kafka's group management is enabled (KafkaConsumer not in consistent region and **startPosition** parameter unset or `Default`), the KafkaConsumer can silently stop consuming messages when committing Kafka offsets fails. 98. As a **workaround**, the consumer property `enable.auto.commit=true` can be used in a property file or app Option.

13 - Add support for transactional messaging
15 - Add support for float32 data type
37 - Update SPLDoc to include 'namespace-info.spl' containing info common to both operators
62 - KafkaProducer: reset handling is confusing
63 - KafkaProducer: reset handling cancel records

Known issues
- When Kafka's group management is enabled (KafkaConsumer not in consistent region and **startPosition** parameter unset or `Default`), the KafkaConsumer can silently stop consuming messages when committing Kafka offsets fails. 98. As a **workaround**, the consumer property `enable.auto.commit=true` can be used in a property file or app Option.

- issue 60 - KafkaConsumer: Potential to lose connection: auto-commit replaced by explicit commit
- issue 67 - KafkaConsumer parameter startTime must document units of measurement. - spldoc update
- issue 70 - Error acquiring permit - avoid false errors on PE shutdown

Both samples and SPL documentation are now included in the release. Now, all samples have a makefile, what allows them to be built without the need to install gradle.

This release contains fixes for issue 53, 57, 58, 61, 65.

This version of the toolkit includes fixes for issue 51.