Add a more generic filing_chars macro

Provides a more generic (and longer-named) macro that (a) allows you to pass in a spec, instead of only using the 245ab, (b) respects the options usually used for extract_marc (:first, :trim_punctuation, :default), and (c) returns the string both with and without the filing characters. I use this a lot for exact matches in title searches (so "The New York Times" and "New York Times" will both get boosted to oblivion)