Plotter:
+ Add overflow check in TransformY.
+ Mark values croosing x axis ("Nullstellen")
+ Mark extremes
+ Mark infinity values.
+ Better positioning of axis description.
  - If no axis position label in the middle.
  - else position label to the side of the axis that has more space to
    the border.
+ Add support for automatic/manual definition of colors for graphs.    

Unit conversion:
+ Implement

Format Conversion:
+ Add support for signed numbers.
