assume_special support for SeriesParser

Flag which, if true, causes any entries with no IDs found to be
flagged as specials.
Add assume_special support to series

Series now accepts option 'assume_special'. If true, will cause any
entries with no IDs found to be flagged and processed as specials.
Also adds support to configure_series and fixes a typo in
configure_series.
Tests for assume_special