Fixed gRPC compilation

After struggling to get gRPC working between C++/Python for about a week, I figured it out:

- need to overload Protobuf headers defined in /usr/local/include otherwise I get the "this protobuf header was compiled with a more recent version of protoc".
- in QT, I can add the helloworld cpp example directory (from gRPC) into the include path, but in order for this to work I also need to add the relevant headers I want to use into the directory.

I have C++ talking to Python now, time to serialize images and send them over.