allow parametrization of Service instances

[shadeofblue]

(within a single Cluster)

[ with regards to Payload parameters, we probably won't want to have a single cluster with services that commission different payloads since then it needs to request separate Demands et al anyway ]

[stranger80]

Maybe we should leverage a concept similar to batch task input data? ie. instead of:

cluster = golem.run_service(
            TurbogethService,
            # payload=payload,
            num_instances=INSTANCES_NEEDED,
        )

have:

cluster = golem.run_service(
            TurbogethService,
            # payload=payload,
            instance_parameters # collection of instance parameter objects 
        )

...where instance_parameters is a collection of parameter objects, each of which would be passed into TurbogethService, either as a param to start() (so that it can be stored in the class field), or via some dedicated init(instance_parameter) method...?

[shadeofblue]

@stranger80 good idea, though, I wouldn't remove num_instances since it by far a clearer way to specifiy multiple copies if one doesn't need to differentiate them