Removing the UI Models in favor of a simple dictionary.

Based on a conversation I had with Will, this is an attempt to make the UI models I want friendlier in serialization, while avoiding storing unnecessary UI attributes in the content store for LMS. 

Deleted the UI Models module, created a nested dictionary, and generally, a bit simpler. 

@wedaly @ormsbee @jrbl  If one or two or you get a chance to review, I'd appreciate it!