Slater determinant brut-force

trialfct (numerical) calculates now the slater determinant and the
jastrow factor for any even number of particles.less than 10.
All calculations like derivatives and ratios of wavefunctions are
calculated using the actual value.

ToDo from here: implementing the same for the analytical case, using
closed form expressions.
integrate class hamilton in class function? Should be called
wavefunction then.