Parametric offset keyhole hook for HSW

This hook allows you to mount objects with those common keyholes on a HSW.
It creates an insert, whith a hook to which you can attach such a hole.
As the distnace between two keyholes is not always a multiple of the distance
between two adjecant Honeycomb fields, it calculates how much this is off and
offsets the hook accordingly.

#### Configuration

* Measure the distance between the centers of the keyholes with a ruler and
put it in `total_width`.

In most cases this should be enough.

However, if your keyhole doesn't look standard, you can do further adjustements:

* Measure the smaller diameter of the keyhole with a caliper and put it in
`keyhole_small_diameter`.

* Measure the larger diameter of the keyhole with a caliper and put it in
`keyhole_large_diameter`.

* `keyhole_small_width` corresponds to the thickness of the material the
keyhole is in. I'm hanging a small parts magazine to my HSW and the metal
sheet of it's casing is 1.5mm t