Add 'redline - paragraph index' to XML node dump

This change adds an output of the 'redline paragraph index' when dumping the
data model to an XML. It also changes the way the paragraph text is dumped
to the XML (it is better viewed in the XML this way).

Conflicts:
	sw/source/core/docnode/nodedump.cxx
Reviewed on:
	https://gerrit.libreoffice.org/6990

Change-Id: I176270047bb4be838972117add5f3588b5573cfe