Show failed tasks as errors in statusbars

Created by: mrnugget

Yesterday I noticed that when executing steps fails in a repository we simply show "No changes" in the status bars. If you execute steps in a lot of repositories that means you'll need to wait until all of them are finished to get feedback on whether one of them failed.

This changes the behaviour from this

to this:

I'm not super happy with the StatusText() and SingleLineError() methods and how to best interface them, but then again I never found wrapped errors easy to manage. If you have any ideas: let me know!