This allows folks to deploy apps that don't have a web process without needing to scale that process down before/after the first deploy. Note that the formations key in the app.json or a manual scale of other processes will be necessary to start anything non-web.
Closes#5700
This change also moves the referenced Procfile out to a host path once on deploy vs potentially several times, which should speed up deploys a small amount and simplify reasoning about the file.
Closes#5112