OpenIAP client c library

This is the rust implementation of the openiap client. This will also function as the "base" for openiap SDK implementations in other programming languages. For now this is only the GRPC client, but the plan is to add a web socket, rest, named pipe and TCP client as well.

lib.rs:

The openiap.client crate provides the Client struct and its methods. For now this only support grpc, will over time have added support for web sockets, http, tcp and named pipes.