Cache handling

[Andrus Adamchik <an...@objectstyle.org>]

I had a few false starts trying to figure out a good strategy for  
cache management that would allow to clear both individual objects  
and related cached queries ... I am making another attempt here:

http://cwiki.apache.org/CAY/refreshquery.html

Basically my current idea is that we should abstract the difference  
between "refresh" and "invalidate", letting Cayenne guess the right  
strategy depending on what information is available. Still raw, but I  
hope to combine all various related API's in a single easy to use  
place. Comments and suggestions are welcomed.

Andrus