Rename IdReference to Id type and set as a parameter the referenced element.
Regenerated aria/client code and fix users' code.

Review at http://gwt-code-reviews.appspot.com/1824803

Review by: skybrian@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11262 8db76d5a-ed1c-0410-87a9-c151d255dfc7