Implement a stdout exporter

[pyohannes]

Implement an exporter that just writes all span data it receives to stdout (or, ideally, to any other configurable file).

A stub for such an exporter is available in the simple example. The stub in the example should be replaced.

[reyang]

Consider a ConsoleExporter with ability to output to stdout/stderr.

[HudsonHumphries]

Hey @reyang could you assign me this issue. I will be working on this in parallel with the Metrics API / SDK.

[HudsonHumphries]

@pyohannes What exactly needs to be added to your implementation in the simple example? I'm currently writing the design document and want to make sure I know what needs to be added. I've added shutdown and timeout functionality, is all that is missing printing more span data?

[pyohannes]

is all that is missing printing more span data?

That is the main part, we want to print all available span data (e. g. attributes, span kind and description).

Then we would need to host it in a dedicated directory (exporters/console maybe) and wire that up in the simple example.

[reyang]

Closed by #183 and #218.