Add an option for unmerging and filling cell values for Excel files. Merged horizontal cells: <table> <tr><th>A</th><th colspan="2">B</th></tr> <tr><td>1</td><td>2</td><td>3</td></tr> </table> Unmerged horizontal cells: <table> <tr><th>A</th><th>B</th><th>B</th></tr> <tr><td>1</td><td>2</td><td>3</td></tr> </table> Merged vertical cells: <table> <tr><th>A</th><th>B</th><th>C</th></tr> <tr><td rowspan="2">1</td><td>2</td><td>3</td></tr> <tr><td>4</td><td>5</td></tr> </table> Unmerged vertical cells: <table> <tr><th>A</th><th>B</th><th>C</th></tr> <tr><td>1</td><td>2</td><td>3</td></tr> <tr><td>1</td><td>4</td><td>5</td></tr> </table>