Add a compatibility setting to disable detection of pen eraser mode

[dgervalle]

I have come across a graphic tablet that has a pen without any eraser mode, but that report all pen contact as being done with the eraser button pressed. As a result, all drawings are erasure, which made such tablet unusable with Storyboarder.

This small pull request add a compatibility section to the preferences pane with an option to disable the detection of the pen eraser mode. This setting is later used to prevent such detection in the sketch pane.

I would be grateful if you could integrate this small improvement.
With kind regards,

Denis Gervalle

[audionerd]

Nice! Thanks for the PR. I'll review this week.

Do you remember which tablet had this problem? Is it something that could be configured in the tablet's settings?

[dgervalle]

I got this issue with a Huion tablet, and no, there was no way in the tablet driver to solve the issue, hence this PR. Would be nice if you can integrate it, since I need to patch any update since then.

[audionerd]

I think it would be more clear to name the preference enableIgnorePointerEraseButtons.

Instead of "Disable detection of the eraser mode of your pen" we could say "Ignore pen buttons" with a hint "Some pen tablet devices always report that their buttons are pressed. Try toggling this if erase mode is always on when you draw."