Same-document paragraph removal too eager

[DavidNemeskey]

remove_same_p.py removes duplicate paragraphs in documents. It is useful when the same content is included twice in an HTML page for technical reasons, such as once for static and once for dynamic presentation, but detrimental to document cohesion when repetition occurs naturally in the text.

Fix the latter case, e.g. only remove paragraphs if all (or most) of the them occur twice in the document.