Add Reviewed status to Study, Experiment, Signature exports

Currently the exports produced by BugSigDB have two variables that appear to track the status of a study/experiment/signature:

State (Possible Values: Complete, Incomplete)
Reviewer (Possible Values: username who completed the review or blank if not reviewed)

While Reviewer implies that the study/experiment/signature has been marked as reviewed, I would like to have a field that directly states that the study/experiment/signature has been reviewed.

From my (naive) perspective, there are two possible implementations:

1. Update the State field to have three values: Complete, Incomplete, Reviewed (not sure if this creates issues if something is both incomplete and reviewed which shouldn't happen but I acknowledge could happen.)
2. Add an additional field called Reviewed with two possible values: TRUE, FALSE (or yes/no or really whatever is easiest)

We have no strong preferences for one over the other so I would say whichever is easier to implement. If there is a different approach, we can consider that as well. We'd like this for all study, experiment, and signature exports.

Thank you.