* Update License header for all source files
- Add Apache 2.0 header to source files that did not have one.
- Update all existing headers dated to 2019 to be 2020
- Remove comma from License header to comply with the Apache 2.0
guidelines.
* Update Copyright notice
Use the standard Copyright notices outlined by the
[CNCF](https://github.com/cncf/foundation/blob/master/copyright-notices.md#copyright-notices)
* setup sdk exporter package
* use sdk exporter package in sdk trace
* use sdk exporter package in all exporters
* empty the exporters list before testing Load
* move SpanData to the exporter package
* use the SpanProcessor registration, don't register exporters
* rename exporter structs to avoid stutter
* rename Syncer and Batcher to SpanSyncer and SpanBatcher
So it's explicit they are for spans, and we reduce the risk of name
conflict
* remove not moot todo
* rename sdk exporter to export
* only execute the SpanData if it is sampled
* rename finish -> end
* missed a few finish -> end spots
* change end back to finish for the bridge span in the openTracing bridge
* fixed grammar, ran make