DocxTableStyleExport: these are expected to be proper strings

And not just random sequences of UTF-16 code units

Change-Id: I6ce18dcb916ea9127693b724f53d14a76e162274
Use comphelper::SequenceAsVector

Change-Id: I0d2c312f903a2a326961430caa772a4841f4fa87
RTF import: fix handling of multiple \lfolevel control words

Change-Id: I242853d491c2ef83f192486fa6fe5a3407700047