ID by row in Csv store

[cjolif]

This quite common in CSV data to not have a field that can represent an ID. In which case this is quite nice to be able to ID by row. This is a feature that dojox/data/CsvStore used to provide and that would be nice to get in dojo-smore/Csv.

[kfranqueiro]

I've added code to support auto-generating IDs if you set idProperty to a falsy value (such as ""). The default is still "id" since it inherits from dojo/store/Memory.

Note that the auto-generated IDs start at 1. As far as I could tell dojox/data/CsvStore starts them at 0, so this is a bit different, but I think starting at 1 makes more sense.