Beta Backyard Kart 0.17.6

This update isn't really that content heavy. However, I was able to spend a lot of time reworking and tuning the welded front suspension.

The vast majority of the work went into weight reduction to finally get the weight and weight distribution closer to reality as well as improve the way the welded front suspension works. The welded front race configs now weigh less than 800 lbs with the heaviest of them weighing in around 780 lbs.

Another large portion of the time was spent getting the lighter wheels and tires to perform better at all speeds (I know this is stupid, but it really makes it more fun to drive when you don't have to worry about the tire setup. They are stable up to 150mph and are much more prone to sliding than skipping, although they will still skip and/or cause a flip if you go into a corner wrong.

The last bit was porting the weight changes to the standard karts and fixing a few issues here and there.

Full list of changes(at least those I remember):

• Frames
  • Standard
    • Welded Front Suspension
      • Significantly reduced the weight
      • Completely redid the beam structure
    • Double Wishbone Suspension
      • Redid weights to match welded front
  • Independent Rear
    • Minor changes to beam structure
• Engines
  • Changed sounds of the 600cc engine
    • It sounds like a cat if an ai is driving it
• Exhaust
  • Reduced number of exhaust parts by consolidating the raised rear and standard exhausts
• Wheels
  • Retuned beam values for the kart wheels
• Tires
  • Retuned beam values for the kart soft tires
• Configs
  • Added missing configs
    • 600cc welded front race
    • 900cc short course
    • Vivace welded front race
    • Autobello welded front race
  • Fixed mismatched and wrongly ratioed diffs