Upgrade to the latest confluent-kafka and update sources accordingly

[lszrn]

From the newly added Changelog:

Added

• This CHANGELOG.md file.

Changed

• The README.md has been updated to reflect all changes below.
• The ca.pem Certificate Authority's self-signed certificate is bundled.
• The example program main.py has been renamed railnova_kafka_example.py.
• The dependencies have been reduced to confluent-kafka[avro,schemaregistry] but upgraded to the latest (2.8.0).
• Usage of the obsolete AvroConsumer API has been replaced by AvroDeserializer and SchemaRegistryClient.
• Settings have been replaced by command line arguments, using the standard argparse module.
• Proper logging has been added, using the standard logging module.
• The program sources are more extensively commented.

Removed

• The requirements.txt file, as dependencies are now reduced to confluent-kafka[avro,schemaregistry].
• The settings.py which were replaced by command line arguments.