Align quantities with Biolink and NMDC

[wdduncan]

In Biolink and NMDC we use a quantity value class to represent quantitative information. In NMDC we have a general attribute value class from which quantity values, text values, images values, person values, etc. inherit. The attribute value class also has a was generated by for provenance info (more such slots can be added).

The advantage of this is that it provides a regular way to add new value types, it is clear that the class represents a value instead of a property/characteristic, and it allows annotate the value with metadata. For example, a quantity value has the following slots:

• has raw value
• has numeric value
• has unit
• has minimum value
• has maximum value

It would good aling how such values are represented across the CCDH, Biolink, and NMDC.

cc @cmungall