#335948 'Installation fails in multi-site environments' by cpliakas

#329886 'Incorrect form_ser_error' by vflirt
added validation for language codes i the sphinx_suggestion module
added  argument in _sphinx_facet_build_facets to allow other values than those from
added  argument in _sphinx_do_search to allow other values than those from
fixed wrong argument for _sphinx_build_advanced_query in sphinx_search_form_submit
general code cleaning