Big pile of updates in order to support rebuilding ingress-models.info

[DeviateFish]

So... a while ago Google Cloud decided to end-of-life the instance the site was running on. By the time I got around to trying to deploy it on a new instance, I discovered that I had been bitten by a pretty severe case of toolchain rot. None of the site would build, and the machine that had the scripts I used in the past was no longer in service... So I decided to upgrade and modernize things a bit, and just start over.

This necessitated a handful of changes here--some necessary, some more just for quality of life when developing on a newer toolchain

• Switch to webpack from grunt
• Move some files to be in more "standard" locations
• Add a Caddyfile for easy hosting for local development
• Switch to yarn
• Update "Inventory Entities" to actually just be nested Drawables, as I had intended (one TODO down!)
• Clean up a couple of the demos to work better
• Add a secondary webpack configuration for a "bundled" build (i.e. minified and all)
• Update eslint rules
• Remove the dependency on es6-promises