WIP: import 3p helpers, introduce webpack to build a single js file

[zackangelo]

What? Why?

This PR contains many changes and is likely to be broken down into several more, but posting diff at the request of @bookernath.

• Introduces webpack to compile paper-handlebars and its dependencies into a single js file for use with the Blackbird experiment.
• Removes any dynamic require statements so webpack can figure out what to include at compile time.
• Introduces polyfills where necessary to remove any dependencies on node.js standard library (most notably url).
• Removes the handlebars-helpers dependency and vendors the necessary helpers in this repo.
• Vendors the Translator class from paper (for no other reason than its required for Blackbird), but also not clear to me why that class is in paper vs paper-handlebars.

How was it tested?

n/a

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cc @bigcommerce/storefront-team