Set fixedDefault of Serial 008[18] and 006[1] and update matchUriToken:
Set fixedDefault of Serial 008[18] and 006[1] and update matchUriToken:

* token 'u' will be used as default
* remove token '_' as a potential uri in favor of 'u'.

libris/librisxl,libris/librisxl,libris/librisxl