Add option to disable touchpad

[ftphikari]

I have a ThinkPad L570 which has a TrackPoint and a TrackPad. I only ever use TrackPoint, so I don't need the touchpad at all, it gets in the way. Here is an interesting thing - I already disabled touchpad in BIOS settings, so it doesn't work anywhere, not on Windows, not on any other distribution, but for some reason it works on Elemenetary. I can't make sense of this. How? Anyhow, I would like for at least one of those 2 issues fixed, either respect the BIOS settings, or add the option to disable touchpad in software. While you are at it, if any of you have a ThinkPad, you can also try adding TrackPoint-specific settings, since no other distro/OS has those, would be a nice touch.