persistence-context-ref

[Dain Sundstrom]

I committed an implemented persistence-context-refs and added some  
tests.  They appear to be working, but next I'm going to hook the CMP  
container up to them to really stress this code. Currently, wrote  
support for extended context but didn't wire them into the stateful  
session bean container yet.

If you are using JPA, I suggest you switch your code to use context  
refs instead of unit refs because the latter are not shared across  
components leading to cache incoherence.

-dain