returning min valid abund_thresh to 0 instead of 1

Initially changed as an idea towards fixing the filtering bug, but
additional explicit checks have been put in place since then, thus
changed range of valid values no longer needed.

R/func.R

@@ -67,8 +67,8 @@ parameters_are_good <- function(annot, count_data_A, count_data_B, boot_data_A,
     return(list("error"=TRUE, "message"="Invalid p-value threshold!"))
   if ((!is.numeric(dprop_thresh)) || dprop_thresh < 0 || dprop_thresh > 1)
     return(list("error"=TRUE, "message"="Invalid proportion difference threshold! Must be between 0 and 1."))
-  if ((!is.numeric(abund_thresh)) || abund_thresh < 1)
-    return(list("error"=TRUE, "message"="Invalid abundance threshold! Must be a count >= 1."))
+  if ((!is.numeric(abund_thresh)) || abund_thresh < 0)
+    return(list("error"=TRUE, "message"="Invalid abundance threshold! Must be a count >= 0."))
   if ((!is.numeric(qbootnum)) || qbootnum < 0)
     return(list("error"=TRUE, "message"="Invalid number of bootstraps! Must be a positive integer number."))
   if (!is.logical(qboot))