Add column for Reviewer & Approver to document reports

[#1]

On document reports, if the document has a proof we need to be able to add a column that shows any reviewers and/or approvers. Ideally for the active proof stage. This will let you build reports to quickly identify who reviewers and approvers are on your active documents/proofs.

You can add an approver column to proof approval report, but since you can't filter proof approvals by project/portfolio/task that doesn't help.