Timewarp Toggle + Improvements

Improved the way Timewarp is implemented by moving the call to
EndTiming, seems to make far more effective use of OVR timewarp
functionality. Allow user to switch timewarp on and off using LSHIFT +
DELETE.
Additional tweak to make the notifications shrink away when they are
finished showing
Splash screen green, easier to read as most games start with a white
splash screen of their own.