Auto launcher & show sensors

[ReadieFur]

This PR adds the functionality to have ovr_test automatically launch with SteamVR. This does however require that the ovr_test.exe remains two directorys above the driver dll but that should always remain there. To set the launch arguments, there will be a file called args.txt which you just specify the arguments as you normally would on the command line.

[mm0zct]

I need to review this properly on a computer to make sure I'll happy with it all, but it looks fine in principle. It does conflict slightly with my personal use mode which is to use the running/not running of the external part as an easy way to not run the driver but it's probably better for most users.

[ReadieFur]

You could always add in a setting to disable the autolauncher, just get the driver to read from the steamvr settings file

[ReadieFur]

My latest commit 0e16b34 adds a basic feature that just displays where the Oculus sensors are in OpenVR space.