Magma computer program for J-groups and exponent polynomials

This is supporting Magma computer code for the paper "Groups G satisfying a functional equation f(xk)=xf(x) for some k in G" by Dominik Bernhardt, Tim Boykett, Alice Devillers, Johannes Flake and S.P. Glasby, see the Mathematics arXiv. The code gives a series of functions for computing with J-groups. In particular it justifies the claim made in Remark 4.12 that Theorem 4.10 holds for c=7 and p>3.