Add alternative download status indicators

[rxvt]

Currently we just print out the object key of each object after it has been downloaded which isn't great as you can't see what objects are currently downloading, only what objects have already been downloaded.

We should investigate some other optional indicators such as having a progress indicator always be the bottom line, something like:

my_pictures/birthday/1.jpg...done
my_pictures/birthday/2.jpg...done
my_pictures/birthday/3.jpg...done
Progress: [########  ]

or perhaps something like what Docker shows you when downloading the layers:

my_pictures/birthday/1.jpg    10%
my_pictures/birthday/2.jpg    100%
my_pictures/birthday/3.jpg    76%