Outdated Dynamic Gravity 0.2

Changes: extended 'Gravity Strength' range, from -100 to 100 (before: 1 to 100, without 0)

Bugs fixed:
1. If you had multiple vehicles spawned, tweaking global gravity leaded to other vehicles gaining the new value.
2. After reloading the vehicle (ctrl + r), it gained both the dynamic and global gravity components.

New advanced setting: 'Calculation Step'. It has two options: GFX and Milliseconds. The latter is in range between 0.5 (2000 hz, precision) and 1000 (1 hz, performance).

When I released the mod, I didn't realize how annoying it is when you select either 'static' or 'dynamic' mode, the vehicle is still pulled down by world gravity. Now vehicles have truly individual gravity settings.