ADD_APPEND_ARGS Adding capability of play apps to take extra args

This pull request is to add capability to smserver to pass in append arguements when starting services. This will allow for more powerful and dynamic starting of services. i.e. it allows for you to override config items

imagine for example that a service is defaulted to point to another service with config accountServicePort=7865, this will allow you to pass -DaccountServicePort=1234 in the list of extra args which would append this config to the service when running it, allowing you to use a stubbed service for example or other non default configurations when starting

I have added two implementations of this
1) for external applications
2) for play services

Other service types do not support this functionality yet
You can use `service_start_request.get("appendArgs", [])` to do the same thing here.