VR Hotkeys Updates, XInput Optimizations, Non-VR Free Look Optimization, Crash Fixes and More.

VR Hotkeys - Added Free Look Scaler.  Enabled VR Hotkeys for any HMD, not just the Rift. Small optimizations such skipping all if statements if g_has_hmd isn't detected and not checking it on every if statement.

XInput Optimizations - Only polls when controller state isn't 0.

Non-VR Freelook - Fixed previous bug that somewhat broke it. Also optimized it to only go through Free Look code when has the view been altered.  "Free Look" checkbox no longer needs to exist for Keyboard/XInput, as there is no performance hit having it on, and it can be unbound if not needed.  Updated description for "Free Look" checkbox that it only affects whether "Mouse Freelook" is enabled.
Fixed crash that occurs when game is started with rift, then stopped, then rift is turned off, then a new non-VR game is started.