Add ES6 module/export support

[perttikasanenhitseed]

It would make it easier to write large and modular applications if the ES6 / Babel had a support for modules and exports.

To my limited understanding, what this probably needs is to compiles something like requireJS or SystemJS with Babel. Module syntax seems to compile OK already now with Workbench Alpha2, but the resulting es5 code fails with missing a require() function for loading the imports.