itemClassificationScheme: Add support for non-item contexts

[jpmckinney]

The Classification block presently has an open itemClassificationScheme.csv codelist for its scheme field. This, of course, only makes sense when the Classification block is used in the context of items. (The definition of the scheme field has "… For line item classifications, this uses the open itemClassificationScheme codelist.")

The Classification block was intended to be used in other contexts, but it only anticipated needing a codelist in the context of items.

I think the solution here is to do something similar to the documentType codelist. That list is used for Document blocks in the context of tender, awards, etc. However, some document types only make sense in specific contexts (as noted by that codelist's Section column).

So, for 1.1.5, I would propose adding a Context (or similar) column to itemClassificationScheme.csv, and then add schemes for organization classifications.

Then, in 1.2.0, we can rename itemClassificationScheme.csv to classificationScheme.csv. (Technically, this is allowed in 1.1.5, but I prefer to do it in a minor release in case anyone hard-coded the filename of the CSV.)

Split from #711

[jpmckinney]

The change to the codelist was removed from #990, as this needs to be merged to 1.1.5-dev instead of directly to 1.1-dev, as it changes normative content. Attaching the patch.

itemClassificationScheme.csv.patch.txt

[jpmckinney]

Relevant comments from #711

#711 (comment) (copied to issue description)
#711 (comment)

[jpmckinney]

Closed by #1033