operator<< for SwPosition/SwPaM/etc. for use with SAL_DEBUG

Change-Id: I99ffa87afa6dbdbd20042a882af428d166546af3
repeated vector::erase() is a bad idea for performance

Especially given that it seems here it was usually called on every single
element.

Change-Id: Ifc5497aac5108481595df80d00c6e00c00f17596
more local variable

Change-Id: Ibe67ecdd5b121ad5624bfd111dca33897d6e1991
allow checking odt docs with assertXPath() etc. too

Change-Id: I01469514372ad5aab8cb81feb5e09f3315162e2a