2.1.8 pre-release: Spin in one spot and finalizing the suspension

This minor update introduces some gameplay improvements:

• While stopped in place, the aircraft will spin around when turning.

• Built-in aircraft performance and suspension have been tweaked.

• The aircraft will now stop when close to fully stopping.

There are also new trees, buildings, and 2 OSTs have been added: "greenshade" and "crater of life"