Webpack

Make building static assets for front end easier by automating all the things and splitting them up

- webpack
- gulp
- split into `priv/ui/app` for source and `priv/ui/public` for actual files for running static app
Good advice. Definitely don't want it published stand-alone.

I'd be just as happy for this not to be an actual node package, but it's really only there for dependency management. Are there better solutions for doing that without going down the whole node package path?

Anyway, will add `"private": true`