Add colliders to Akita axles

[Wyzard256]

The Akita core and flatbed parts have no collider around their wheel axle:

This makes it awkward to assemble an Akita "in the field" using KIS, because KIS only snaps to a part's attachment nodes when the mouse is over one of the part's colliders. To attach the wheels to an Akita, you have to orient the camera so that the axle attachment nodes are "in front" of the collider box. That's not difficult if you know that it's necessary and you have a mod that shows the colliders, but it can be pretty frustrating otherwise — it feels like the KIS node attachment just randomly doesn't work sometimes, for no apparent reason.

The Akita cab has a collider on the bottom that ends up sitting just above the wheel axle when attached to the front of the Akita core. It might be OK to remove that collider if the core part gets one around its wheel axle.