refextract: Series letter & INSPIRE title output improvements.

• '--inspire' or '-s' will output $s content in the INSPIRE format: %(title)s,%(volume)s,%(page)s,%(year)s as opposed to the INVENIO format: %(title)s %(volume)s (%(year)s) %(page)s which is still default.

• To cope with the INSPIRE format, dynamic recognition of series letters has been added. It was previously relying on the kb to provide series letters (lent on by IBID title repetition). The series letters are paired with the volume of a journal title for INSPIRE compatibility. However, the journal kb can either have the series characters hard coded into it, or just the pure titles. Refextract will handle both cases successfully.

• Improved series letter recognition of IBID's by extending [A-H] to the standard: [A-H]|I{1,3}V?|VI{0,3}

• Removed whitespace, print statements.

• Sorted an undefined variable 'kb_line_num', fixed with enumerate().

• Added author group numeration to the 9996C field.