Wood frames [CR]

Closes #5328.

Adds wooden vehicle frames, which have the simple trade-off of being half the weight of a steel frame but also have half the durability. They can be crafted with 2x4s and nails, and break into splinters when destroyed. Allows for making lighter, faster vehicles.

Feedback would be appreciated on if the half-and-half tradeoff is fine or if it should be adjusted in one direction or the other.