Add single_row method

[ElenaStrashko]

Add this method, because it's a convenient way to create treetables with a lot of rows using Python. Like this:

            .treetable([
                    {'display_text': 'name', 'type': 0, 'unit': 'this is a name'},
                    {'display_text': 'value', 'type': 0, 'unit': 'This is value'}, ])\
            .single_row(0, [[1, 2], [3, 43]])\
            .single_row(1, [[1, 2], [3, 43]]) ```

[CLAassistant]

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