[Grace-core] Class Encoding

[James Noble]

> This allows for classes to be implemented within the language, while
> still allowing concatenation (as opposed to delegation) as the method
> for inheritance (http://portal.acm.org/citation.cfm?id=219264, cited
> by Andrew Black on the wiki).

Andrew

> This is a lot shorter than your encoding, seems simpler, needs no hidden methods, and works for const fields.

ahh, I'm going to agree with both of you - Andrew's encoding is simpler and more general,
while Eric's may well --- be a better description of a sensible implementation scheme e.g. on the JVM :-)

James