Fix selection mode

[ibdafna]

Signed-off-by: Itay Dafna i.b.dafna@gmail.com

This PR reverts the changes from commit 4a685fc as they break the selectionMode parameter of BasicSelectionModel, resulting in 'cell' selection regardless of the parameter passed to the constructor:

new BasicSelectionModel({
    dataModel: model6,
    selectionMode: "row", // won't work
  });

That change was arguably not needed to begin with as 'cell' selection mode will select full rows or columns when they are clicked on.

[blink1073]

Thanks!