miscutil: fixes translate_to_ascii

* translate_to_ascii() checks the characters one by one in order to
  make sure unrecognized values are ignored ("" instead of
  printing "[?]").

* Adds unit test for this case.

Tested-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Federico Poli <federico.poli@cern.ch>
bibindex: adds tokenizers for parent records

* Adds BibIndexExactAuthorParentTokenizer, internally it calls
  BibIndexExactAuthorTokenizer.

* Adds BibIndexAuthorParentTokenizer, internally it calls
  BibIndexAuthorTokenizer

* Hardcodes in bibindex_engine that the tokenizers of the fields 'exactauthor'
  and 'author' want a record id insthead of a tag value.

* Sets BibIndexExactAuthorParentTokenizer as tokenizer for the
  'exactauthor' index (tabfill.sql and upgrade script)

* Sets BibIndexAuthorParentTokenizer as tokenizer for the
  'author' index (tabfill.sql and upgrade script)

* Adds tests