Remove a candidate.
C = sudoku_candidateremove ( C , kind , iv , jv , v )
a 9 x 9 cell of candidates
the 9 x 9 matrix of number candidates
set to 1 for row, 2 for column and 3 for block, 4 for cell
the row of the value. If kind = 1 or 4, iv in 1:9. If kind = 3, iv in [1 4 7].
the column of the value. If kind = 2 or 4, jv in 1:9. If kind = 3, jv in [1 4 7].
the value to remove
Removes the value v from the candidates in C. Removes v from the row, column or block identified by ix and jx. If kind = 1, we remove v from the row iv. If kind = 2, we remove v from the column jv. If kind = 3, we remove v from the block (iv,jv). If kind = 4, we remove v from the cell (iv,jv).