Recipe and tooling for webpack-like bundling

[daveaglick]

Consider a recipe and additional modules or tooling (such as an MSBuild task) that would make it possible to use Wyam as a webpack-like bundler for front end development. Wyam already needs to do much of the same kind of work for site generation, so this would just encompass the parts specific to JS/css/less/sass/etc. Would need to think about how to handle CommonJS module definitions. Also sourcemaps and other JS trickery.