Load car parameters from a file

[juzzlin]

Load car parameters used in Tire and Car from a config file, e.g. JSON.

Hi. I discover your game by chance: it's very fun to play and the physics & the CPU are fair, so I've just signup github for this. The track editor is great but to have a way to change the car's parameter (or better, to have several types of cars) would be definitely awesome.
Congrats for DustRacing2D and thanks for sharing it :)