Add page to change desktop overlay translation

The implementation is simple 3D vector scaling and addition. The
HmdMatrix34_t consists of a 3x3 rotation matrix and a 3D vector for
position.

The overlay position is only updated whenever a new overlay is changed
because we need the old overlay position in order to modify it. The
openvr call to get the position is only updated whenever you open the
menu.

A new page was created due to lack of space on the utilities page.

src/overlaycontroller.h

@@ -39,6 +39,7 @@
 #include "tabcontrollers/UtilitiesTabController.h"
 
 #include "openvr/ivrinput.h"
+#include "openvr/overlay_utils.h"
 
 namespace application_strings
 {
@@ -121,6 +122,7 @@ public: // I know it's an ugly hack to make them public to enable external
     SettingsTabController m_settingsTabController;
     ReviveTabController m_reviveTabController;
     UtilitiesTabController m_utilitiesTabController;
+    overlay::DesktopOverlay m_desktopOverlay;
 
 private:
     QPoint getMousePositionForEvent( vr::VREvent_Mouse_t mouse );