This function is to be called before any other actions.

Fix update issue.

Preliminary fix issue in previous commit.

Use the "real" bit depth even for 16bit images by setting the sBit
attribute in the PNG format.

Problem: Bit depth is set in inherited class which is actually not known
here....
Partly closes #15.

Change to Atkinson algorithm for lambda>100. Closes #14.

Add LV unit to Simulation/Rotation property.

This makes working with different bit depth much easier.

Save/Load is not yet working correctly!!!

Simu base class now return NaN as pixel size.