Some small updates

Remove unused dz keywords for 2D reconstruction function
Default to 3D version for DirectEventReconstruction
Show discrete reconstruction solutions

For a station (4 detectors), show the possible arrival directions for
arrival times in discrete steps of 2.5 ns.
All possible combinations of arrival times with steps of 2.5 ns are
created and reconstructed.
Results (zenith, azimuth) are shown for the different combinations of 3
detectors.
And the layout of the station is shown.