v2: Add basic 3DOF Index Controller support
Only the "gen1" watchman usb protocol is supported (almost same as vive wand).
Note: Lighthouse v2 data is not properly ignored, the IMU data is only parsed correctly
when controller is not hit by lighthouse lasers.
Supported:
* trigger value
* trigger button
* trackpad x, y
* trackpad touch
* thumbstick x, y
* thumbstick click
* system click
* a click,
* b click
Not supported:
* trigger touch
* touchpad force
* thumbstick touch
* system touch
* a touch
* b touch
* grip squeeze
* finger tracking
