Include DescriptorFields (method parameter metadata), indirection to support dynamic resolution (EJBs)

Greetings!

I'd like to submit my changes upstream, since I'm about to publish a cdi extension which can publish cdi and jee beans as MBeans in another repo, and figured it would be worth pushing this upstream.

The layer of indirection was added so that alternative implementations can resolve delegates from proxy info (say, JNDI lookups in the case of EJBs) and done in a manner that shouldn't harm the operation of the core library.

Regards,
-Bryan