Table row / col insert issue (#5583, #5673)

Modified the ```cloneCell()``` method to take a boolean value (children) that will clone child nodes.

(this defaults to true to keep current expected functionality)

```insertRow()``` and ```insertCol()``` then modified to call ```cloneCell()``` with ```children = false```

This enures only a clean ```<tr><td>..</td></tr>``` element is copied

I can only find 2 issues that are cause by this, but I am sure there is more.

- http://www.tinymce.com/develop/bugtracker_view.php?id=5673
- http://www.tinymce.com/develop/bugtracker_view.php?id=5583