Restructure and add web player

The web app now has two main pages: "builder" and "player". Each has its
own views file. We'll also need a home page at some point.

The player is adapted from older code written in Flask/jQuery rather
than AngularJS. We might reconcile these a bit in the future.

Stopped using Flask to serve Angular's partials, since that was silly.

Modified the engine's game data parser to take file path strings.