bugfix - fixed up the SecondOrderNonSymplecticState integrator such that
it produced the correct numbers. This also made it symplectic, hence the
class name change (removed "Non"). This is now the one I will use.
init - added lots of other attempts at making better integrators, which
eventually failed, producing mostly first order or diverging higher
order integrators.
improved - enhanced the QFTSandbox to also handle changing time steps
(dt) without recalculating the entire Hamiltonian (which takes forever).
Also removed the real time changability, but this will be reincluded.