InsetOld::hasParagraphs->InsetOld::numParagraphs

[Alfredo Braunstein]

Can I do it?

hasParagraphs is never used in the code, and we need numParagraphs for
having PosIterator/Cursor::operator-- 

PS: should I drop PosIterator and try to make Cursor::operator++/--
operative?

Alfredo