[EM] new revised ranked pair method in matrix form

[Ross Hyman]

Candidates are classed in two categories: Winners and Losers.  Initially, all candidates are Winners.  C_i is the ith candidate.  A matrix M contains how many times candidates have defeated each other.  The element M_ij equals the number of times that C_i defeats C_j.  Initially M is the Identity matrix. 

The pairs are ranked in order.  The winner is determined by affirming each group of equally ranked pairs in order, from highest to lowest.   Affirming is composed of two steps: Matrix Multiplication and Reclassifying candidates.    

Affirming Step 1: Matrix Multiplication
Create the matrix D where D_ij  = 1 for each C_i > C_j that is to be affirmed at this rank.  D_ij=0 otherwise.  Replace the old M matrix with the new one: M + MDM.

Affirming Step 2: Reclassifying
Each winner C_j is reclassified as a loser if M_ij >M_ji and C_i is a winner.

The count can be ended before affirming all pairs if one winner remains.