writerfilter: drop support for simple list types without constants

In other words, from now it's a must to map ST_Foo simple types to
NS_ooxml::LN_something constants, and raw integers (which are hard to
grep and hard to track down where are they used) are no longer an
option.

Change-Id: I968b27bca3f64f6f4a382b87e2dbc499a3132ea2