Support microdata output in Views, Panels, etc

Problem/Motivation

HTML data formats usually rely on the fact that properties are nested within the HTML tags of items in order to express the relationship between an item and its properties. However, if a site uses tools like Views or Panels to move fields around independently, microdata can't depend on that nesting.

This is also an issue if themers use something like page_alter to move fields outside of their containers.

Proposed resolution

In order to support Views and Panels, we could possibly place items as meta tags at the bottom of the page and use the itemref feature of microdata to set the relationships.