Completely remove features related to Desktop Overlay

As of SteamVR 1.10.1 the overlay width feature has been implemented by
Valve in the standard settings.
OpenVR features related to overlay translation have been removed and the
main reason for including them (multi monitor setups) have been solved
by Valve giving each screen an individual overlay.

src/overlaycontroller.h

@@ -42,7 +42,6 @@
 #include "tabcontrollers/VideoTabController.h"
 
 #include "openvr/ivrinput.h"
-#include "openvr/overlay_utils.h"
 
 namespace application_strings
 {
@@ -163,7 +162,6 @@ public: // I know it's an ugly hack to make them public to enable external
     SettingsTabController m_settingsTabController;
     UtilitiesTabController m_utilitiesTabController;
     VideoTabController m_videoTabController;
-    overlay::DesktopOverlay m_desktopOverlay;
 
 private:
     QPoint getMousePositionForEvent( vr::VREvent_Mouse_t mouse );