NTR 'has characteristic value' and 'characteristic value of' for handling qualitiative and quantitative values

[ddooley]

This issue is to support a pull request for object properties 'is value of' and its inverse, 'has value' as found in pull request #844 . More usage information is at https://qqv.ontodev.com/primer.html#changes-to-assay-modelling

'is value of' is defined as: "Is a relation between a characteristic (c) and another characteristic (ca) of a given entity in which (c) is a categorical kind of (ca) or is a scalar or count representation of (ca).

[wdduncan]

Please see comment about is value of.

[ddooley]

I have tweaked relationship names: now "is value of" is "is characteristic value of"; and "has value" is now "has characteristic value"