Add a debug_writer, line-oriented output

I've found this output format very useful -- easy to scan and grep through. Each field on a line; multiple values separated by pipes. Obviously not as useful if you're outputting binary marc...

I pulled the generic parts of JsonWriter into a new "LineWriter" class and use it in both DebugWriter and JsonWriter. JsonWriter's public interface is unchanged.

Example output:

```
bib_2710183  author2_unstem            Edward S. Herman and Noam Chomsky ; with a new introduction by the authors. | Chomsky, Noam.
bib_2710183  author_display            Herman, Edward S.
bib_2710183  author_facet              Herman, Edward S. | Chomsky, Noam
bib_2710183  author_sort               Herman, Edward S.Manufacturing consent : the political economy of the mass media / Edward S. Herman and Noam Chomsky ; with a new introduction by the authors.
bib_2710183  author_unstem             Herman, Edward S.
bib_2710183  discipline_facet          Language & Literature
bib_2710183  format                    Book | Print
bib_2710183  id                        bib_2710183
bib_2710183  isbn_t                    0375714499 | 9780375714498
bib_2710183  language_facet            English
bib_2710183  lccn                        2001050014
bib_2710183  material_type_display     lxiv, 412 p.
bib_2710183  oclcnum_t                 47971712
bib_2710183  pub_date                  2002
bib_2710183  published_display         New York
bib_2710183  publisher_t               New York : Pantheon Books,
bib_2710183  source                    traject_test_last
bib_2710183  subject_t                 Mass media Ownership. | Mass media and propaganda.
bib_2710183  subject_topic_facet       Mass media Ownership. | Mass media and propaganda.
bib_2710183  text                      Herman, Edward S. | Manufacturing consent : the political economy of the mass media / Edward S. Herman and Noam Chomsky ; with a new introduction by the authors. | Manugacturing content | New York : Pantheon Books, 2002. | lxiv, 412 p. ; 24 cm. | Updated ed. of: Manufacturing consent. 1st ed. c1988. | Includes bibliographical references (p. [331]-393) and index. | A propaganda model -- Worthy and unworthy victims -- Legitimizing versus meaningless third world elections: El Salvador, Guatemala, and Nicaragua -- The KGB-Bulgarian plot to kill the Pope: free-market disinformation as "news" -- The Indochina wars (I): Vietnam -- The Indochina wars (II): Laos and Cambodia -- Conclusions. | Mass media Ownership. | Mass media and propaganda. | Chomsky, Noam. | Contributor biographical information http://www.loc.gov/catdir/bios/random051/2001050014.html | Publisher description http://www.loc.gov/catdir/description/random044/2001050014.html
bib_2710183  text_extra_boost_t        A propaganda model -- Worthy and unworthy victims -- Legitimizing versus meaningless third world elections: El Salvador, Guatemala, and Nicaragua -- The KGB-Bulgarian plot to kill the Pope: free-market disinformation as "news" -- The Indochina wars (I): Vietnam -- The Indochina wars (II): Laos and Cambodia -- Conclusions.
bib_2710183  title1_t                  Manufacturing consent : the political economy of the mass media /
bib_2710183  title2_t                  Manugacturing content
bib_2710183  title_display             Manufacturing consent : the political economy of the mass media /
bib_2710183  title_sort                Manufacturing consent : the political economy of the mass media
bib_2710183  title_t                   Manufacturing consent :
```