Add unblinding mechanism to all tasks that need it.

This PR adds a parameter unblinded to tasks inheriting from POITask (which are almost all tasks need to perform some kind of measurement). To perform the unblinding, three changes are required per task.

1. Change the underlying combine command to obtain observed results.
2. Store the result in a file with a slight different name (injected "unblinded" to the path).
3. Update plotting methods.

Supersedes !18 (closed).