writerfilter: move include to the implementation

Change-Id: I27b3c5276c5bfd1a29d8edadc6078c71cfbf2609
writerfilter: no need to include QNameToString in dmapper

All dmapper handler classes inherit from LoggedProperties, which takes
care of logging already, and QNameToString is only useful to turn the
numerical IDs into dmapper token strings.

Change-Id: I437f2c815293caeda0dabbe65cf9458ae5a60566
writerfilter: move QNameToString to the OOXML tokenizer

It's filled with contents in the OOXML tokenizer anyway, keeping its
interface outside of it is pointless.

Change-Id: I10051c5b41a1247417bfb3dd3170a76bf20925aa