[MERGE] Output refactoring and XML integration into bzrlib

[Aaron Bentley]

Aaron Bentley has voted abstain.
Status is now: Waiting
Comment:
I still have no idea what the XML output of this is meant to look like, 
and I suspect it's too imitative of the user-facing output.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C2422be180711161810m7c88a6bfy3daf12d3fb7863a9%40mail.gmail.com%3E