This initializes default values in the display, distortion and IMU
properties so the runtime is happy in case the JSON config could not be
read.
This patch also moves default value initialization for the Index
into one place with the others, for cases we do not have the data.
This adds a driver for the Vive family of devices based on Philipp
Zabel's ouvrt.
The driver currently only handles the IMU and main board report streams,
but is able to acquire the JSON configuration and utilize it for IMU
calibration as well as distortion configuration.