ear alt-dd should be able to specify module alt-dd external to the ear file #31

The spec currently requires the ability to provide an alternative deployment descriptor
for an ear file when deploying the ear file. The alternative deployment descriptor will
NOT be packaged in the ear file, to allow overriding the application's deployment descriptor
without modifying the application package.

However, the spec does not describe a way for that ear-level alternative deployment descriptor
to reference module-level alternative deployment descriptors that are NOT packaged in the ear
file. There should be a way to do this.

One approach would be to specify the alternative deployment descriptor as a jar file that
could contain both an application.xml deployment descriptor as well as module deployment
descriptors referenced by alt-dd elements in that application.xml deployment descriptor.