Finishing implementation of ListViewAdapter.  An extensive test class will be submitted in a later change because the rest relies on API changes that haven't been submitted yet.

Review at http://gwt-code-reviews.appspot.com/636802

Review by: jgw@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8305 8db76d5a-ed1c-0410-87a9-c151d255dfc7