Option to keep duplicates in Table visual

In most cases it's a nice feature that duplicates are automatically removed, but in some cases you also need the duplicates.

For now we use a workaround by adding an index to the table, set the name to an empty character and make it so small users won't notice it's there.

Steps for the hidden column:

- Rename it using a whitespace character‎;

- Go to "Specific column" and make the font and backgroundcolor white;

- Go to "Values" and disable "Text wrap";

- Make the column as small as possible.