Fix PS4 Controller Input

Summary

As found while investigating issue #683, there is at least one PS4 controller type where mapping to Gamepad input fails. The issue is rooted in the OpenTK dependency and potentially Windows only.

How to reproduce

• Ask @SirePi for the exact controller brand and model that reproduces the problem, but also check different PS4 style controllers for issues.
• Run the Input Handling sample and observe joystick and gamepad input.

Workaround

• Using the SDL backend of OpenTK by copying an SDL2.dll into the working directory is a workaround for the launcher - but not the editor, as SDL has no editor support.
• There are third-party tools that can map any controller to an XInput device on Windows. However, this is a user workaround, not a developer workaround.

Analysis

• Screencaps of the problem:
  • With SDL: https://gfycat.com/DescriptiveEthicalCub
  • Without SDL: https://gfycat.com/CreepyFabulousCoypu
  • Without SDL, the mapping is off, one of the triggers is mapped to a sticks Y axis and vice versa.
• As the controller mapping is detected correctly, the issue is not caused by a missing or mismatched mapping entry in the database.
• It could be incorrect handling or interpretation of axis / button HID device data.