TinyMCE: fix the More and Next Page tags behavior:
- Append them inside top level <p> tags.
- If the caret is not in a top level <p>, create new paragraph after the current top level tag.
- Do not change placement when edited in the Text editor.
See #27378
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git-svn-id: http://core.svn.wordpress.org/trunk@27566 1a063a9b-81f0-0310-95a4-ce76da25c4cd