Differentiate between server and client plugins

[pks-t]

We should differentiate between server and client plugins. Server plugins are plugins providing a service's functionality to clients as well as providing the logic of being invoked. Currently, when being invoked, the service simply uses the current client logic, which should be specific to the command line.
The client plugin will be comprised of the current client handling function. The server plugin will have to provide another new method which handles the case when the server is being told to invoke another service.