INTEXT-111 Allow PP for Kafka producer context

 - Remove hard coded names for bean names at the producer context parser
 - Fix and update tests
 - Remove the use of `BeanFactory` to get the producerConfigurations in
KakfaProducerContext and use setter to set the producerConfigurations
 - Add logic to send the message from producer configuration when there
is no header specified for the topic and single producer configuration
is used.
@artembilan sorry about the code style issue. It would be helpful if you could fix that change on merge :-) thank you!