This function is called by RankAggregator::consensusRanking.
The upper bound value is the value used by the branch and bound
algorithm in determining whether or not to replace the current incumbent
solution.
upperBound(ccr, umat)a vector of rank positions that is a candidate complete ranking
a matrix, which is either the output of evaluationMatrix,
or a subset of the output of evaluationMatrix.
A numeric value for the upper bound of a candidate complete ranking