Switch to webpack workflow

A set of changes to match Blip and Clamshell's front-end workflow with Webpack.

@cheddar Do you want to take a look and tell me what you think? Thanks!
Platform portability is one argument, however there are a other unix things we use elsewhere so I'm not sure it stands.

Being able to use JavaScript functions and Node.js modules is another advantage, although it doesn't show up here.

I'm struggle with bash (yesterday I couldn't even figure out how to do "if this env variable is not set"). But if you'd like to rewrite `buildapp.js` and `buildconfig.js` in Bash, be my guest :)