Add Standard Size Presets for Regular, Counter-Bore, and Counter-Sink Holes

[jmwright]

A preset drop down could be added at the top of the controls that would have presets like 4-40, 1/4-20, M4 and M5. Selecting one of those would fill in the other controls with standard measurements. Things like slip fit tolerances need to be considered, somehow. The presets could be stored in a JSON file that is part of the release package. Maybe something like the following.

{
  "CounterBore": {
    "M4": {"hole_diameter": 2.1, "cbore_diameter": 2.4, "depth": 2.1},
    "M5": {"hole_diameter": 4.2, "cbore_diameter": 5.0, "depth": 4.2},
  }
}