Custom format string or number of decimals for progress.

[wischi-chr]

At moment the progress is rendered as an integer (or at least I couldn't find the option to change that).
For a long running task (~1h) the progress doesn't really change for a long time.

I'm currently using a second progress bars to how the fraction part. 2.47% looks like this for example:

It's ok, but obviously not very pretty. Would be great if there were a way to show more decimals.