urth-viz-table support for multiple item selection

[lbustelo]

Currently tables support single item selection only. Would be nice to have it also support multiple item selection.

I suggest that we do the following. By default, the table should support single selection. Selection should always be returns as an array regardless to make things easier on templates.

We would add a boolean property called multi-select that turns on multi selection.

<urth-viz-table selection={{sel}} multi-select></urth-viz-table>

/cc @peller @aluu317

[aluu317]

It looks like Handsontable currently does not support discrete row selection, but it's in their plan to implement it for the future: https://github.com/handsontable/handsontable/issues/2119 and https://github.com/handsontable/handsontable/issues/1831

[lbustelo]

@aluu317 Those hansontable issues are all closed. What should we do here then?

[aluu317]

Here's the link to their feature request, this feature is currently listed as number 97 (under consideration, but has been approved): https://github.com/handsontable/handsontable/wiki/Feature-requests I'm not sure when it'd be moved into their milestones, but for now, I guess we could close this issue?

[lbustelo]

Leave it open to track

[peller]

when implementing this, the multiSelect property in charts should be moved to urth-viz-selection-behavior and shared with urth-viz-table. Selection is now an array of arrays only for multiSelect=true See #285