Change json schema to avro structure again

This time I think I got it at last. Phew.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Add Avro array predicate and writer

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
JSON Schema to avro: start testing

And fix an obvious bug.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Json schema to avro: add tests for array

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>