Deciding when to and when not to deduplicate repeated direct formatting
of paragraph / character properties is stricky, this bug is about a case
when deduplication should happen and did not, since commit
1970a686 (tdf#113408 RTF import style
dedup: separate paragraph and character handling, 2017-10-31).
Especially that deduplication works in both directions: it should remove
properties which are duplicated and also should insert explicit default
values for not repeated properties.

Fix the problem by making the getDefaultSPRM() aware of the context
(which style type it deals with), and then by making sure that only
default properties relevant for the given style type are inserted.

Change-Id: I35b6599cc47fa51b8754fd921c61a3b31a283547
Reviewed-on: https://gerrit.libreoffice.org/60946Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins