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!
And I actually disagree, I can read this as "there are cases in which the form should be disabled: the user is not authenticated, the browser is not compatible, or there is an upload in progress". It makes sense to me :)