f, a ring element that is a non-zero divisor in the ring of I
Outputs:
a sequence where the first item is a ring map from the ring of I to a presentation of Hom(I,I) = 1/f(f*J:J) and the second item is a list consisting of the fractions that are added to the ring of J to form Hom(I,I).
We use this in integralClosure to complete a key step in deJong's algorithm. Interested users might want to use this to investigate different choices for f in the algorithm.