Move the jaeger thrift http exporter from core to contrib repo

[objectiser]

Description:
This PR is to enact action item 3 from open-telemetry/opentelemetry-collector#618 (comment). Not sure if possible to preserve history, but this code was copied from here.

Link to tracking Issue:
Related to open-telemetry/opentelemetry-collector#618

Testing:
Uses existing tests copied from core repo.

Documentation:
Text from exporter README (jaeger thrift http section) has been extracted and added to a new README in the exporter's folder.

[objectiser]

The testbed is currently failing due to the duplicate exporter for jaeger_thrift_http. Should I change the contrib exporter to jaeger_thrift?

[pjanotti]

@objectiser just to be 100% sure: no actual code changes just taking the files as they are.

Regarding the error, we can rename it temporarily so we can do the merges on the repos independently, but before we release and tag another contrib we go back to jaeger_thrift_http that requires a new tag on core (to be done after the receiver is removed from there). The alternative is to remove first from core publish a new one and then merge this one. I prefer to do the former @tigrannajaryan @owais

[objectiser]

just to be 100% sure: no actual code changes just taking the files as they are.

@pjanotti Yes that is correct.

[pjanotti]

It actually LGTM @objectiser, just setting as "request changes" so we can coordinate correctly.

[pjanotti]

@objectiser could you please push a change with jaeger_thrift so we can clean the build? This way we get ready to merge this one.

[pjanotti]

LGTM, could you please rebase @objectiser

[objectiser]

@pjanotti @owais ready to review/merge.

[objectiser]

@pjanotti @owais please review/merge, thanks.