Moves the separate quiet variable in the `Config` struct into the existing
verbosity field; the `Verbosity` enum now has a `Quiet` variant. When running, the
presence of the quiet flag will set the verbosity to `Quiet`, overriding any
number of verbosity flags in the CLI args.
Make line continuations strip leading spaces on the next line.
This changes what is passed to the shell, so this is a breaking change.
However, I don't think that this will break any recipes.
