Adding procfile_structure on app api

[Cryptophobia]

The /app route should expose the procfile_structure of the app release. Since the structure on the /app route is not indicative of the actual deployable processes of the application, there should be another json structure that can tell us what the procfile is actually set to for the latest release. When using procfile_structure we can tell which of the processes exist in our procfile at this particular release:

The idea is that we can use procfile_structure for scaling and validating which processes we can actually scale through the /scale route. This is so because a call to .../app/{app_name}/scale with a payload {"worker": 1} would actually fail with 404 Not Found and this return from the api:

{
    "detail": "Container type worker does not exist in application"
}

Our app structure is below:

    "uuid": "db58126d-a76b-428c-9741-1b8d09bed2b7",
    "id": "testing-application-procfile",
    "owner": "admin",
    "structure": {
        "worker": 0,
        "newone": 0,
        "scheduler": 0,
        "web": 1,
        "testing": 0
    },
    "procfile_structure": {
        "web": "node server.js",
        "test": "node server.js"
    },
    "created": "2017-08-15T15:32:27Z",
    "updated": "2017-08-15T17:12:12Z"
}

But a call for each of the processes in procfile_structure would not fail the scale call.

This has been tested extensively with git remote application deployments and Docker image pull deployments.

The tests are not written yet.
Code in deis-cli has not been written yet.

[Cryptophobia]

This PR is related to this upstream PR:

deis/controller#1321