Support of workflows

[tarekelgindy]

Often it can be nice to define the layers that a stack will use externally of the code.
Something that I ended up doing for another project was to create a "workflow file" that would list the layers being used and their arguments. This is different from the json file for a stack in that it's quite simple and doesn't include a lot of the extra information that is included, making it easy for a user to create manually. For example:

{
    "workflow_name": "Sample Workflow",
    "layer_library": "layer_library",
    "stack_library": "stack_library",
    "input_file": "data/sample_input.json",
    "output_file": "data/sample_output.json",
    "layers":
    [
        {"layer_name": "do_nothing", "kwargs": []},
        {"layer_name": "do_something", "kwargs": [("sample_arg","1")]},
        {"layer_name": "do_something_else", "kwargs": [("another_arg",2)]},

    ]
}

What are your thoughts on this?