Allows for creation of tables with contents manually entered by users
(i.e. spreadsheet style), so that users can create completely custom
tables.
Supports control custom cell contents, foreground and background colors.
For the c++ api dox this expands to "\c nullptr" (the
\c directive indicates a code literal value), and for sipify/Python
it expands to ``None`` (`` is sphinx annotation for literal values)
Makes for nicer dox for both c++ and Python!
