Cleans up some dead code, revise comments and TODO's

Router: InboundMessageDistributor: Remove commented-out useless check
Router: RefreshRoutersJob: make EXPIRE private
Router: CapacityCalculator: delete commented out section for G cap handling
Router: FloodfillNetworkDatabaseFacade: update TODO, if fromLocalDest is null and isClientDb is true in a call to FNDF.search throw an IAE, clients should not use exploratory tunnels
Router: FloodfillNetworkDatabaseFacade: remove commented-out chanceOfFloodingOurOwn call
Router: FloodfillNetworkDatabaseFacade: remove commented-out chanceOfFloodingOurOwn