Fix ImageBundleBuilder so that it de-deduplicates identical images.
Adds the gwt.imageResource.maxBundleSize system property if an end-user needs to override the maximum sprite size.
Ensures that the ImageResourceTest is run without data inlining on systems that inline by default.

Patch by: bobv
Review by: rjrjr


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5097 8db76d5a-ed1c-0410-87a9-c151d255dfc7