GlassFish v2 supports SplashScreens using a vendor specific deployment
descriptor described in http://docs.sun.com/app/docs/doc/819-3672/geqwd?a=view.
Java 6 supports SplashScreens using the MANIFEST.MF entry "SplashScreen-Image".
It makes sense to replace the GlassFish specific deployment descriptor method by
Java 6's standard method.
GlassFish should use the SplashScreen found in the MANIFEST.MF entry unless it
is overwritten in the vendor specific deployment descriptor.
This removes the need for the programmer to supply deployment descriptor, if
it's sole use is to provide the splash screen.