Split Bill of Materials into "Shopping List" and "Assembly List"

[jon-harper]

The BOM needs to be fully disambiguated to a Sales BOM (purchased items, lit. materials) and a Manufacturing BOM (finished parts for assembly).

Notable issues:

• Heat set inserts should be in the materials category
• Cut-to-length parts like PTFE, weatherseal should have a fixed entry in materials and another with length from the parts list.
• Cables should all get part numbers of a new category in the form CN123, as none are modeled and all are default values; some are purchased and others fabricated.

[jon-harper]

I've reviewed how other projects do this, even though I'm aware of the Sales/Manufacturing terms. I like Jubilee's approach of a "Shopping List" and then a Bill of (finished) Materials for assembly.

This will take some work on rescripting the input data, possibly into several CSV files to allow more flexibility with columnar data per type.