refactor dependencies in bundles and widgets

[erichanson]

Right now, widgets have dependencies in the widget_dependency_js table, which fk's to widget and dependency_js. Then HTML resources often times import bundles which contain widgets and can then be called in. Also sometimes Javascript resources are stored not in the dependency table but rather as a static resource at /js/whatever.js. Bundles sometimes depend on other bundles' data, but there's no concept of dependencies between bundles. Refactor all of this.

Foremost, bundles need dependencies. Then, when a bundle depends on another bundle, they import it with a short-name alias, and can reference it throughout the bundle as such.

Then, maybe when we have server-side rendering of templates, we can just auto-generate the bundle import lines at the top of each HTML page? Regardless, that way dependencies are guaranteed to be met.