Progress bar / more verbose logging

[bennahugo]

De cal graph has been running for about an hours now and there has been no output. Perhaps there should at least be a progress bar? :)

[JSKenyon]

There was a progress bar but between it and the existing logging, the terminal was becoming a mess. I still don't have a great solution for this, although I could put in some comforting "alive" messages for users if a chunk is taking more than say 5min to process.

As a random aside, I am not sure of the scale of your data here. An hour on a single chunk suggests that it is quite large - did you have the solver.threads option set? It exists for cases where you have few chunks (<dask.threads) but still want to use as much computing power as possible.