Improving "HMD not full screen" behavior

[firstmustburn]

Not sure if this repo is being actively maintained, but since it is a top search result, adding this for anyone who might come after me.

With the HMD device as it is in the repo, when you alt-tab (or some other times, I'm not entirely sure when), the window will turn red and you'll see a headset offline error until you click back on the VR view window.

I found that if you add these lines:

	vr::VRProperties()->SetBoolProperty( container, vr::Prop_IsOnDesktop_Bool, false );
	vr::VRProperties()->SetBoolProperty(container, vr::Prop_DisplayDebugMode_Bool, true);

in the activation of the HMD device, then you no longer get these errors and the HMD display window interoperates with windows much better.