Add the root optimiser to ground-state reverse-engineering algorithm

[DrMattHodgson]

If the current algorithm is used to find as an initial guess for the ground-state potential – perhaps a residual of 1e-5 – then root will be able to reduce the residual done to ~1e-15. This will be 1) faster and 2) more consistent with the time-dependent reverse egineering algorthm which will hopefully add some stability.