[Spreadsheet] Composite cell values

[enridaga]

Currently, cell values are limited to simple datatypes such as number, string, boolean. However, sometimes cell include richer content, for example, links. We could apply the facade to such content and make those links accewssible.

[luigi-asprino]

Could you post an example?

[enridaga]

I created a test and developed a basic transformation (which should be reviewed for consistency, some decisions I am not 100% sure)

[enridaga]

The general point is to support the case where cells require a complex description, I have added a property spreadsheet.composite-values that makes the cell be triplified as a container rather than a literal value.

[luigi-asprino]

I also made the triplifier extract comments that might be attached to the cells

[luigi-asprino]

I've also updated the documentation https://github.com/SPARQL-Anything/sparql.anything/blob/v0.9-DEV/formats/Spreadsheet.md#spreadsheetcomposite-values

[enridaga]

I think this seems ready to go, I will move it to v0.8.1