Add support @property. Fixes #3

For properties not exposed as attributes (published properties), this differentiates. Otherwise, it's confusing that everything is listed as an attribute. Users will expect they can configure that property as declaratively using its attribute.

Reviewer: @sjmiles 

![screen shot 2014-05-07 at 9 48 06 pm](https://cloud.githubusercontent.com/assets/238208/2911977/0890e6f8-d66c-11e3-8141-739a7e48d33f.png)

I didn't touch the compiled core-component-page