[REQUEST] Addition of a measurement conversion node

**Is your feature request related to a problem? Please describe.**
I like to do precision modelling and generally setup my scene to use metric units (CM). Sometimes though I have a need to model in imperial units such as a 9/16 bolt or a 2x4 board which has no simple metric conversions.

**Describe the solution you'd like**
I would like a node that I can enter a specific value in any unit and get a value that is translated to the current unit set up. When I want to extrude or inset by a very specific amount it would be handy to have it handled by this type of conversion node.

**Describe alternatives you've considered**
I currently do all of the math myself and find myself taking liberties with the rounding, and it usually ends up with badly mid aligned faces/verticies until I go back and do a proper conversion.

**Additional context**
Just a random thought I had. Should apply to degrees/radians as well and any other units blender has?