* 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)
* Add global propagators
The default global propagators are set to the chained W3C trace and
correlation context propagators.
* Use global propagators in plugins
The httptrace and grpcplugins should also get some API for setting a
propagator to use (the othttp plugin already has such an API), but
that can come in some other PR.
* Decrease indentation in trace propagators
* Drop obsolete TODOs
Now we do "something" with correlation context - it ends up in the
context, and we put the context into the request, so the chained HTTP
handler can access it too.
The other TODO was about tag.Upsert which is long gone.
* Do not unnecessarily update the request context
The request context already contains the span (and we add some
attribute there), so inserting it into context again is pointless.
Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>
* Initial skeleton
* Revert noop provider removal
* Checkpoint
* Checkpoint
* Implement Bound instrument and LabelSet
* Add test
* Add a benchmark
* Add a release test
* Document LabelSetDelegator
* Lint and comments
* Add a second Meter test; fix typo; add a panic
* Add a test for the builtin SDK
* Address feedback
