[Delivers #82528174] Playlab Embeddable iFrame

This feature allows any iFrame to be embedded into e.g. a multiple-choice assessment question.
It also creates a stripped-down embeddable format suitable for embedding Play Lab games into a small frame:
![image](https://cloud.githubusercontent.com/assets/56541/5022316/e121f948-6a97-11e4-854f-969189dd347e.png)


think it would look cleaner to use .present? instead of ! .blank? (same below)