Added a new diff tool, updated for Java6

The inline HTML classes allow a user to specify inline CSS styles instead of classes. The main benefit of this is:
A) remove dependency on an external stylesheet
B) make the result suitable for e-mailing *.

* Most notably, gmail will not accept external stylesheets and only inline CSS. The result that is generated is accepted and rendered by gmail.

I also updated the code to use Generics where possible and updated build.xml to remove ant warnings and updated the java target/source version to 1.6