Given a sparse matrix A over a ring S having m rows and n columns, and another ring R, return the m x n sparse matrix over R obtained by coercing the entries of A from S into R.The argument order to ChangeRing(A, R) here is consistent with other forms of ChangeRing, while the SparseMatrix(R, A) form of this function is provided to be consistent with the sparse matrix creation functions above, for which the destination ring is the first argument, if supplied.