Implement String.contains and associated test. Also fix typo in StringTest. Issue: 1729 Patch by: rovrevik (minor touchups by jat) Review by: jat, tobyr (desk review) git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1733 8db76d5a-ed1c-0410-87a9-c151d255dfc7