Part Wheel Installation Handler

# Installation Handler Overview
Name: Wheel Installation Handler
Function: adds the ability to install parts as vehicle wheels into vehicle slots
From FVTM: yes

This Installation handler allows you to install a part as wheel into
the vehicle's WheelSlots. You can enter here various settings of
the wheel for it to get only installed into matching WheelSlots.

Offset and other calculations are automatical from the values you specify
here and the values which are configured in the vehicle's WheelSlots.

Example config (taken from FVP, take a look there for more examples):

{
    "__comment": "Part JSON file.",
    "Installation":{
    	"Handler": "wheel",
        "Removable": true,
        "Radius": 8, "Width": 4
    }
}

Here an overview of the available fields:

• Handler - the id of the wanted handler, it is wheel
• Removable - (boolean) optional, if the part can be afterwards removed from the vehicle
• Radius - radius of the wheel (circle radius) in "pixel/texel" (16th of a block)
• Width - width of the wheel
• Connector - connector size, e.g. if 2, will only install on wheelslots with size 2
  if leaving empty, defaults to 0 (zero)
• Tireless - default true, if the wheel has a tire already included (e.g. when importing old models)