KM full text search using sphinx.

Use "NO ZODB" approach - i.e. search results are delivered entirely by MySQL backend together with text excerpts from Sphinx search engine.

See http://www.erp5.org/HowToUseSphinxSE

In order to make Sphinx return snippets one needs to manually do in a MySQL shell:
> CREATE FUNCTION sphinx_snippets RETURNS STRING SONAME 'sphinx.so';