Specify language for CSV to JSONLD importer

[straleyb]

We would like to find a 'slick' way of describing languages for CSV to JSONLD. We could add it as another piece of information in the header label:string@en or a new column in the CSV language:symbol. Or for each cell, have the language specified there (just in case maybe a title is in a language but the alt label is in another language.

[wickr]

I think per-column is pretty clear, with English as a default. The graph should be able to handle multiple columns/methods just fine. And I think the 'string' part can be dropped, so language could be added like:

label label@es label@de