Inconsistent impl of Rosbridge Protocol in `Service` class

[drewhoener]

Service#callService sends the op message

const call = {
      op: "call_service",
      id: serviceCallId,
      service: this.name,
      type: this.serviceType,
      args: request,
      timeout: timeout,
};

which adds in type: this.serviceType.
As far as I'm aware, the Rosbridge protocol doesn't specify this field when calling a service (ref)

[EzraBrooks]

There's a number of places where this is a risk because of the object going straight into the Ros class which is obviously happy to accept anything that meets the minimal rosbridgemessage interface. I think we should add private members to each class that wrap the call in the appropriate type for that particular class, personally