add "only pen" support

[Wladefant]

remove the finger paint support and only paint with a pen. Or put it in settings where you can choose between pen support OR finger and Pen support.

Right now even while I am drawing I often draw with my skin

So I want only the option to draw with a pen. When doing something with a finger, for example the option of moving an object could be added

[personalizedrefrigerator]

See #46 (comment)