[merge] don't use 'dots' progress output on non-interactive runs

[Aaron Bentley]

Aaron Bentley has voted +0.
Status is now: Waiting
Comment:
I don't think renaming DummyProgress is a good idea.  Not all our 
progress indicators are bars, and even our default progress bar can be 
configured as a spinner instead.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3Ce01316480707110029g4bdf42e3i1a29f848150fee75%40mail.gmail.com%3E