bnc#880448: Improved handling of placeholder shapes

If subTitle placeholder is not found, try body instead of title.
And use body text styles instead of title, for subTitle.

Also improve PPTShape::findPlaceholder to find placeholder
with just nSecondSubType type without the same index.

(cherry picked from commit 2a7119021edea8346e4673d57cac3f051a5d0968)

Conflicts:
	oox/source/ppt/pptshape.cxx

Change-Id: I470e7268088eb989fb934007dfcf704f67d8cb1d
Reviewed-on: https://gerrit.libreoffice.org/11065
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>