BibIndex: support for CJK languages

* Introduces new tokenizer: BibIndexCJKTokenizer.
* Adds CJK search support in search_unit in search_engine.
  (closes #285)

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>