cvar cleanup

-Added vr_autofov to allow overriding of VR provided default FOV
-Renamed vr_hud_bounce_func to vr_hud_bounce_mode
Fixed issue with FSAA

-Fixed issue where enabling FSAA when it was started disabled caused
screen corruption
Fixed issues related to pausing and VR mode
-Menu's now pause the game again
-Pausing the game retains head tracking
Add auto FOV setting to VR menu
Disable bicubic by default