Specification Draft Started

Following Chris' work to set up bikeshed I've started a draft of the
specification:

   - Currently can be found on the 'objects' branch:
   https://github.com/w3c/PFE/tree/objects
   - I've added an outline of the expected sections.
   - Thus far I've added a draft of the specification text that defines all
   of the data types used in the patch subset approach.

I can review what I've done so far and we can discuss further at tomorrow's
meeting.