Common module build script and tooling clean-up

[jaronheard]

What

For the new packages added in #1200:

• [x] Reexamine common scripts & tooling that is shared across packages
• [x] Bundle packages more compactly (either using rollup or webpack) & clean up bundle scripts
• [x] Adjust generators to allow custom placement of new components

See https://github.com/hackoregon/civic/pull/1200#pullrequestreview-422433476 for additional detail

Why

Follow up from #1200

[jaronheard]

Note: The common scripts and tooling are working fine for now. In #1214, I added a watch script for the new component packages, so that you can rebuild components across packages. At some point, we could pull up some scripts to a common scripts directory, but I think it's fine for now.

When investigating bundling packages more compactly, I was getting better results with our current build system that just uses Babel, then I was with the Rollup configuration I started testing in. With our current build system, code-shaking is working well in basic configurations like Gatsby and create-react-app. I fixed an issue with code-shaking for ui-core in #1210