Zipkin exporter must support Zipkin v1 JSON format

[codeboten]

As per spec: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/sdk_exporters/zipkin.md#considerations-for-legacy-v1-format

[robwknox]

@codeboten i'll pick this up if you want to assign to me

[codeboten]

Done, thanks!

[robwknox]

Changes are prepped in 1173_zipkin_exporter_v1_json_support but are dependent on #1318 being merged before a PR can be created.

[robwknox]

Staged PR to give better view of changes while awaiting merge of #1318