footPrint -- generalized footprint function of an ideal

Returns the value of the generalized footprint function of the ideal I on the parameters d and r. Given an ideal I, a monomial is called standard of I if it is not a leading monomial of any polynomial of I. The parameters d and r are used as follows. The function computes the degree of the ideal generated by sets of r standard monomials of degree at most d. The footprint function is a lower bound of the generalized minimum function genMinDisIdeal. More information about the footprint function can be found in Definition 1.3 at https://arxiv.org/pdf/1812.06529v1.pdf