New features

• update apache-avro to version 0.17 adding support for nano resolution timestamp logical types in schemas
• Added graphite-plaintext tremor codec to support the graphite plaintext line protocol

Fixes

• gbq connector naming is now gbq_writer as it is documented
• fix gbq connector url missing /
• fix GELF message-id from auto-increment to random-id in postprocessor/gelf_chunking.rs