Use gRPC

[pavolloffay]

User gRPC between agent and collector. We could also consider using it in client libraries to report data.

See:
https://groups.google.com/forum/#!topic/jaeger-tracing/toBNkL_zEDE
#526 (comment)

[jpkrohling]

Just to make it explicit: based on what was talked on the last week's Jaeger meeting, this is not about removing Thrift, but about adding gRPC.

[isaachier]

See jaegertracing/jaeger-idl#41 for potential first steps.

[Falco20019]

Would love to see that happen. Took me a couple of hours to generate jaeger-idl for .NET Core since the code generator for 0.9.3 does not include .NET Core but the NuGET packages are all 0.9.3 newest... finally found a working package on GitHub (not NuGET...)

gRPC would have been a lot easier, and I already have the runtime included. Would allow me to remove thrift runtime.

[yurishkuro]

Superseded by #773