Need to be able to do ps:scale commands

[odscjames]

Otherwise have to set in app.json
https://dokku.com/docs/processes/process-management/#manually-managing-process-scaling

And then you can't change it later.

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We also don't want situation where any deploy changes a value that might have been tweaked on the server. For now, this is a useful feature on dev server but don't use on live.