Collection display names

Adds a collection `displayName` to collection.json, to override the one in config.json. For instance, allow an epic story collection to be temoprarily titled "NSA Scandal" etc.

![tool](https://f.cloud.github.com/assets/1147913/1131656/9840b3a6-1bbd-11e3-8943-123c6baee94f.png)