More DAGfile formatting options

[JoshKarpel]

We should have some more options, mostly for making them more human-readable if need be. Some requested options:

• Print the VARS on separate lines for each key/value pair, instead of all on one line.
• Add empty lines between sections, layers, etc.

[bbockelm]

Why should this be an option and not the default?

[JoshKarpel]

🤷‍♂ , I don't have too strong an opinion on that. But some people may have different definitions of human-readable, so I think we should choose reasonable defaults on whatever formatting options we provide, but leave them as options. These options may also have implications for people who have existing DAGfile parsers (for example, maybe it can't handle the VARS being separated).