fix bugs with NA translation from DF, fix bug with svyby call using na.rm.by and na.rm.all params, and use multicore speedup; TODO: benchmarking
fix bugs with NA translation from DF, fix bug with svyby call using na.rm.by and na.rm.all params, and use multicore speedup; TODO: benchmarking

semanticbits/survey_stats,semanticbits/survey_stats