[WIP] Move MeterProvider to API

[eddynaka]

Fix #579

[MikeGoldsmith]

Thanks for the start @eddynaka.

I agree with @cijothomas's comments in the issue and maybe the issue wasn't overly clear. The purpose of the issue was to move the API specific components to the API level, things that are the building blocks so if someone wanted to create an alternative SDK, they could do so.

I think we should put a pin in this one until @cijothomas's coming PRs are complete and we can review what should be in the API.

[eddynaka]

@MikeGoldsmith , yeah, i talked with @cijothomas about this. i will probably close and wait for his PR.

Thanks again! :)