Adds full justification, undo, and redo options to RichTextArea.  These options are widely supported in all modern browsers.

Patch by: jlabanca
Review by: jgw
Issue: 1211, 2185



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5630 8db76d5a-ed1c-0410-87a9-c151d255dfc7