Protobuf WebSocket API

Usage:

1. Put your protobuf files into a protobuf folder under your project.
2. [Server] Run pwa load-schema to load Protobuf schemas.
3. [Server] Write API functions and declare input output types.
4. [Server] Run pwa generate-services to generate Protobuf services definition.
5. [Client] Run pwac generate-api to generate client side API endpoints.
6. [Client] Write client side code with generated APIs.