Windows and Mac Store update

Support Apps from Windows Store and Mac App Store.

Once again we've moved more logic from server-side to client-side, reducing the capability of an individual ctools platform plugin. So, this will break existing add-on platforms. However, these add-ons still should have the hooks they need to get things done. In particular, you can override/extend the app_link.getPlatformKey method to add your custom platform regex check.

Refactored & Tested

We've overhauled the front-end logic to be very testable. Eventually, it may be split out to it's own Bower component.