Add PDF output support

[bertyhell]

Recently i rewrote the drawing to canvas system to use a drawingController.
The specific implementation of drawing controller can now be chosen.
Currently the screenCanvasDrawingController exists.
But to support pdf, we could also add a pdfDrawingController that changes the functions of the DrawController interface to draw to a dpf file.

The required functions to implement are quite limited:

• setLineStyles
• clearCanvas
• drawLine
• drawArc
• drawArrowHead
• drawText
• drawImage