Apache Avro schema output option

[benstroud]

This is a suggestion for improving the current Apache Avro output support. It would be nice to have a way to also output to a JSON file the Avro schema associated with the Avro data file.

- In the output tool, provide a file browse option to optionally write out the Avro schema JSON file

- Introduce a new tool or function to extract an Avro schema document from an existing Avro file and then save it to JSON