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.

Closes #9.

This should now be handled by the application code (e.g. CamActor).