Support unselect for Stack- and Grid-based tables

[reedes]

Presently there is no way to unselect a row, other than to select another row of the same table.

Ideally this will work like the native single-select for List tables.

[reedes]

This is similar to the hover issue, #35, and will likely require a similar solution.

[reedes]

Opted for simple tap to select/unselect for Stack and Grid based tables.

Creating separate ticket for more advanced selection mode for these table types.