Performance fix, no more bloom in VR, add a setting for speed control

- Performances were downgraded in previous version, it should now be fixed.
- In VR, picture looks shimmered, like with oily glasses. It was the bloom effect that was added in flat screen and VR version. But as it's a camera lens effect this doesn't felle natural at all in VR. So it's removed.
- In last version, speed close to surface was far more slower. It was to make the flight easy for everyobiody. But the modification was actually frustating for many, so there is now a "speed close to surface" setting so it should make everyone happy.