Wait tasks (like provide signature) should be automatically aborted after a configurable time out

Many developers don't bother aborting the workflow or the provide-signature work request when they notice an error and have to prepare a new upload anyway. Or when it was just an experiment.

While that's not a practice that we want to encourage, it would still be better to somehow cope with it and auto-abort the wait task when the user failed to provide a signature in a reasonable delay.

I suggest that the base model of all WaitTask have such a configurable timeout in their task_data (so that we can manage it with task-configuration mechanism).