Replaced HasKey with ProvidesKey and moved it from Column/NodeInfo to ListModel. Updating SelectionModel to use handlers and have only one setSelected method, firing events in a finally command to avoid multiple view updates.
http://gwt-code-reviews.appspot.com/307801/show

Review by: jgw@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7866 8db76d5a-ed1c-0410-87a9-c151d255dfc7