Shaping v2

[philrz]

We've finished a first version of the shaping functions, but there's still debugging that needs to be done and rough edges smoothed out to make it useful enough to blog about or recommend to users. At some point we'll also want to make shaping a more prominent feature within the Brim app itself.

For the "Data MVP0" milestone, we're currently imagining that it'll be ok for us to not yet try to build a rich app UX for building/using/managing shaping configs. Rather, for "data users" in MVP0 who drag their generic data into the app, we can somehow call their attention to shaping as a feature of the platform, linking out to article(s) that walk through shell-based examples of shaping data which they could then turn into ZNG for import into Brim or export as other formats like Parquet for use in other systems.

Therefore, the issues linked to this Epic are marked for the MVP0 milestone so we'll have to confront which ones make the cut, with the understanding that we'll decide to let some roll to MVP1 or beyond. Thus far #2122 is one that's considered likely to be treated as a priority to get into MVP0.