Update to the Note reflecting changes to Microdata.

[gkellogg]

This version simplifies the algorithm to use more concepts from the current Microdata draft and eliminates the creation of document-relative properties.

• Algorithm simplified to take advantage of more explicit steps described in [[MICRODATA]].
• The content attribute is processed on all HTML elements.
• Property Value section is simplified to leverage equivalent in [[MICRODATA]].
• is simplified to leverage concept of current vocabulary from [[MICRODATA]].
• The evaluation context as been removed, and memory is global.
• The mechanism for creating document-relative URIs for itemprop tokens for untyped items has been removed.

It's a pretty substantial simplification, and could be simply used as a section in the Microdata spec obsoleting this note.

cc/ @danbri @chaals @iherman

[gkellogg]

See https://rawgit.com/w3c/microdata-rdf/v3/index.html for a formatted version of the spec (pr-preview doesn't seem to be doing the job).

[iherman]

@gkellogg I am fine with the proposed changed on the text, and merging this PR. My only caveat is that I am currently on vacations, ie, I cannot feed that back into my implementation for further testing; I plan to play with that (and other possible software issues) in August which will may be a slow month anyway.

[gkellogg]

Test Suite currently includes test for relative property URI generation, which we can mark as obsolete at some later time. I haven't removed the logic from my implementation yet.