[Checkers] Demo tests

[Mahmood Ali]

Greetings Mike,

 From skype:
> Also, it would be great to have regression tests for the demos  
> (using diff files to check expected before and after results

I have finally gotten around to doing this.  The ant build file for  
each demo project has a test target that validates the demo  
automatically.

The scripts currently only work if the projects are clean check-outs;  
otherwise the diffs might get confused.

Regards,
Mahmood