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.
* Add configuration for number of digits after colon.
* Axis labels should not be covered by grid lines

Format Conversion:
* Add support for signed numbers.

FunctionInput:
* Add more functions
* Make constants a table
