Sample with other than normal incidence angle

Implement the possibility to have the sample not at normal incidence but at an angle:

• sample lines and etch lines are taking into account the incidence angle
• beam propagation takes into account incidence angle on sample. Beam propagation is calculated as intersect between line passing through zone plate corner point and focus point and sample plane. This simplifies and systematize the calculation a lot.
• thanks to new beam propagation, focusing of zone plate 0th order by KBS is now calculated as well

Overall though, the influence of the sample incidence angle is found to be minimal is nearly all relevant cases besides very grazing sample incidence angle.