Sets the cell contents for an existing cell.
If the given indices do not exist and autoGrow
is TRUE then the given row and/or column is
automatically added. If autoGrow is
FALSE, then an error is returned.
int $row -
Row index
int $col -
Column index
mixed $contents -
May contain HTML or any object with a toHTML() method
string $type -
Cell type either 'th' or
'td'