Register models on the run, rather than in the workspace

[ant0nsc]

At present, all models are registered in AzureML by Model.register. This means that from the list of models we can't have a reference back to which run generated the model.
Instead, in AzureML runs, register the models by run.register_model. Caveat here is that the API does not allow child paths, hence have to copy into a separate folder.
For runs on the commandline, continue to register by Model.register.