Mark proposals/candidates as rejected

[mzur]

If a proposal/candidate is manually "unselected" in the refine view, it should be permanently marked as "rejected". A rejected proposal/candidate is visually dimmed in the select and refine views (similar to converted candidates). However, a rejection can be reversed.

The dimmed proposal/candidate should be made visible again on mouse hover in the select view. There could be a button to undo the rejection there.

Similarly but unrelatedly, converted candidates could be made visible again on mouse hover in the select view.