Make task failure more elegant

[ktran9891]

Issue:
When tasks fail, they do so inelegantly. In other words: We ignore them. And when our Cron goes back to do it again, it fails over and over at the same task. This was fine before, but these tasks start to snowball and bog down our workflow. This manifests into us trying to perform feedbacks on the same hundreds of adsorption sites with many failing over and over again for things like QHulls.

Current state:
If a task fails, we see the next-nearest-dependency failure.

Desired state:
It would be great if our logs simply ignored dependency errors for tasks that are still going through FireWorks. It would also be great to get the root non-dependency-error[s] to pop up upon trying to execute a task and then have that task emailed to us. Then we could try to fix it or give up/flag it as "broken" somehow, and then GASpy would know to start ignoring that task.

[ktran9891]

The recent refactoring addressed this. The new Luigi version actually addresses most of this, as it gives a much more useful traceback and log file now. And the QHull errors are now gone, too.