Implement plotting of statefunction at constant azimuthal coordinate for linearly polarized case

[x] Implement this method as a member of qprop.wavefunction.Wavefunction object.
[ ] Try to make this plotting routine as a separate function and let this method be a wrapper of the actual routine function.
[ ] Implement decalcomanie argument of the complete bisection of a sphere in real space.
- For this, the number of phi grid points should be even to get an exact bisection. For example, if the constant phi coordinate was set as pi/2 than the other phi coordinate against which the state function of that side should also be plotted is pi/2 + pi = 3/2 * pi.

jam31118 / qprop