Support anonymous Table columns without header text

It would be useful to provide support for anonymous columns, or column renaming with support to define empty name. Maybe `Table.Columns.CustomName`.

Use case: order notification with following fields:

- **description** (name of item, plus details, variant,.. ),
- _anonymous_ **price per unit** of measurement (e.g. `14€ / pc`, `19€ / liter`, `5€ / kg`,...),
- _anonymous_ **amount** (e.g. `2 pcs`, `4 liters`, `32 kg`,...),
- **price** contains `price per unit * amount)`.

I don't really want to display names for price per unit and amount columns. These headers prolong the width of these columns, as header is wider than content. And, it's the meaning of the column pretty much obvious from the content of fields..

No file or test is named. Search the repository for the Table implementation and column naming APIs, including the proposed Table.Columns.CustomName, then inspect related tests; done means columns can render without visible header text while existing named columns continue to work.

Written by the indexing model from the issue text.