Add server/client codegen options to protoc
Add server/client codegen options to protoc

Implements support for specifying additional options for `protoc` gRPC codegen to exclude client and/or server code.

Usage:
```
protoc TestEvent.proto --swiftgrpc_out=Client=true,Server=false:.
```

grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift,grpc/grpc-swift