[DX] Add a Production/Development Toggle to core.

This is something to consider for the future. Respective issue/discussion over at d.org: https://www.drupal.org/node/1537198

JavaScript is typically used in two forms. There is the production and development version. The development version is used for development, troubleshooting, bug fixing, when you need to step through execution, etc. We should provide a toggle to allow switching between production/development JavaScript.

A simple implementation can be found in the speedy module.

This is a setup task to start shipping with minified JavaScript files in addition to the development version. The naming for production/development is taken because this is the naming convention used on jquery.com.