Protoc: let users decide if the plugin should generate clients, server or both

[tsegismont]

The protoc plugin is not configurable. Consequently, it generates code for clients and servers, forcing users to add dependencies to both vertx-grpc-client and vertx-grpc-server.

The plugin should be configurable, in particular it should be easy to switch off code generation for clients or server from Maven.

[tpalan]

Also, usually a vertx server is either a client or server for a specific API specification, and not both.

[vietj]

in vertx5 there are three plugins to let this possible choice

[vietj]

• VertxGrpcGenerator
• VertxGrpcClientGenerator
• VertxGrpcServerGenerator

[vietj]

so perhaps we can close this for 5.0.0 :-)

[tsegismont]

Fixed by 52d18fa