i think it would make a nice addition to be able to plot multiple lines in the same Cartesian.

what i think needs to be done for this:

• extract line drawing to sub-class
  • the subclass could be an self contained bitmap or group (what makes more sense here?)
  • change to add point function
  • add draw or update function (what is the better naming here?)
  • color option
• handle multiple Plot-Classes

please let me know what you think!