Add support for Avro single-object encoding

[ByteMaDo]

We use KDI for one of our customers, who sends Kafka messages via the Avro single-object encoding specification.
This pull-request introduces support for this encoding type.

Implementation details:

• Our client does not (nor want to) utilize a schema registry. As a result, this implementation supports one or more provided schema files instead.
• The implementation requires apache-avro version 0.17.0 or later due to a bug in the fingerprint calculation in earlier versions.

We’re happy to address any feedback or suggestions to improve this pull-request further.