Add Kafka import additional consumer properties

[morazow]

An additional useful properties for the Kafka consumer application:

• MAX_POLL_RECORDS: The maximum number of records returned in a single call to poll(). The default value is 500. Since we perform a single poll() each time the udf is run, users can increase this value to import more records from partitions on each udf run.

• FETCH_MIN_BYTES: The minimum amount of data the server should return for a fetch request. If insufficient data is available the request will wait for that much data to accumulate before answering the request. The default setting of 1 byte means that fetch requests are answered as soon as a single byte of data is available or the fetch request times out waiting for data to arrive. Setting this to something greater than 1 will cause the server to wait for larger amounts of data to accumulate which can improve server throughput a bit at the cost of some additional latency.

• SSL_ENDPOINT_IDENTIFICATION_ALGORITHM: The endpoint identification algorithm to validate server hostname using server certificate. Default value is https. User should be able to set this to empty string ("") if they want to disable host identification while using secure connection to Kafka clusters.

[morazow]

Fixed in #43.