Input abstraction layer

[dogtopus]

Might be helpful for future addition and modification for input methods.

Current wishlist:

• Buttons
  • GPIO input
  • External IO board
  • Emulated buttons (via e.g. touchpad/slider, analog sensors)
• Touchpad
  • Hardware-independent position report and gesture recognition
  • Must support single/double flick for gesture recognition
  • Must support mapping coordinates to e.g. touchpad
  • Slider modes should sit on top of the AL (and not be a part of it)
• Should be relatively scalable. Should be easy to add new types of input if desired (e.g. analog sticks, sensors)
• Preferably event-driven (maybe get some inspirations from existing systems like evdev and Windows event system/dinput/whatever?)

[dogtopus]

We can probably adopt Eventually Teensy EventResponder for the last and the second-last part.

[dogtopus]

Since the input is no longer remappable, this became unnecessary. Input "abstraction"/remapping can be done at compile time.