Buggy Game v29 - Better accessibility

Buggy Game was always supposed to be hard as nails, but I do see it turns off a lot of players, at least initially. So I decided to change some of the default values to make the game a bit less unforgiving. Also, I added the possibility to change the damage multiplier.

By default, damage is now half of what it used to be, CPU skill is set to 90% instead of 100%, and the camera is zoomed out a bit more.

As a bonus feature, I've added slipstreaming; as you drive behind another car, you will profit from having less air resistance, which can help with overtaking. However, the opponents also have this same advantage when driving behind you!

Full changelog:

- lowered default CPU skill to 90%
- decreased default zoomlevel for better foresight
- decreased default collision damage twofold
- added slipstream effect (configurable)
- slight physics tweaks, should improve pure fwd/rwd cars mostly