This adds a --jaeger flag to dolt CLI which installs a Jaeger Tracer as the
global opentracing Tracer. The Tracer is configured to report to an HTTP
collector running on http://localhost:14268, which is the port that docker
image `jaegertracing/all-in-one` listens on.
Also adds some parameters in places where Dolt constructs sql.Contexts to pass
the correct Tracer through.
Also adds a few new Span points, in things like nbs.Get and
metaSequenceImpl.getChildSequence.