octofit progress bar interacts poorly with jupyter notebooks

[sefffal]

Raised on slack by @hessek1:

Currently running octofit in a Jupyter notebook produces hundreds of pages of progress output, because the progress bar is not cleared from the screen.

We don't have a lot of control over this, but should find some solution to prevent this. There is a python function available that can clear a current cell, but maybe there's an even simpler option, like reducing the frequency of updates to once every 10 percent or so.