[MERGE] Restore a working UI implementation suitable for emacs shells.

[Vincent Ladeuil]

Ping reviewers.

I just want to mention that without that patch bzr.dev crash:

bzr: ERROR: exceptions.AttributeError: 'CLIUIFactory' object has no attribute 'note'

and that makes my life quite miserable as it means I can't run
bzr.dev *nor any derivative of it* (as in any bug fix branch)
under an emacs shell.

      Vincent