Add a serializer class for AVRO.

[SeanSolberg]

Add a new serializer class to add support for the AVRO serialization format.
https://avro.apache.org/

This serializer is a bit tricky because it requires a schema in order to read and write the stream. The schemas can be stored at the beginning of an avro file or they can be stored externally. This is a bit different than the other serializing techniques that are inherently self describing and thus don't need the concept of a schema in order to serialize.

[SeanSolberg]

This serializer has been started and is included in the checked in code. However, It is not fully baked yet, but it is under active development.