Revive samples/expenses from its 2.3 breakage. Also now generates
sample data on demand.

Review at http://gwt-code-reviews.appspot.com/1447809

Review by: jlabanca@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10237 8db76d5a-ed1c-0410-87a9-c151d255dfc7