false positves for conflicts

[JuliaLawall]

The interface for reconciling PC conflicts and author conflicts allows confirming conflicts, but doesn't allow indicating that a conflict is a false positive. Likewise authors should be able to indicate and provide reasons for false positives, so the chairs know whether or not the authors have considered the conflict recommendation.

[tzimmermsr]

+1 to allow the chairs to hide conflicts that are false positives. When there are many false positives it is hard to discover newly found conflicts when PC members update their collaborator lists.