Add rake task to replicate current backlog and exit when empty

I think a ruby-progressbar to give status would be a lot more effective.  You could also change the sleep time to perhaps 1 second to give better feedback without it flooding the screen.

Something like...

```ruby
unless (total = RrPendingChange.count) == 0
  ...
  require 'progressbar'
  pbar = ProgressBar.new("Backlog", count)
  ...
  until (count = RrPendingChange.count) == 0
    pbar.set(total - count)
    sleep 1
    ...
ensure
  ...
  pbar.finish
end
```