Convert serialization format of parsers to Avro
Currently external parsers use json as format to serialize events. This is portable and human readable, but inefficient. avro should be used instead. This has two sides, a python one, and a scala one.
A preliminary avro protocol definition is in https://gitlab.rzg.mpg.de/nomad-lab/nomad-lab-base/blob/master/core/src/main/avro/ParseEvents.avsc