include the standard deviation of "inbreeding" measurements

this adds $.diversity.e to the output of inbreeding load and input of inbreeding plot to show errors bars in the final plot.

these can be discarded by running something similar to

inbreeding load $experiment
    | reject diversity.e
    | inbreeding plot --options { k: $OPTS.k }

bins/inbreeding/load.nu

@@ -13,7 +13,7 @@ def get-experiments []: nothing -> list<string> {
 
 export def main [
     experiment: string@get-experiments, # something of the form '<seed>-<env>'
-]: nothing -> table<strategy: string, diversity: table<x: int, y: float>> {
+]: nothing -> table<strategy: string, diversity: table<x: int, y: float, e: float>> {
     let exp = $experiment | parse "{seed}-{env}" | into record
     if $exp == {} {
         error throw {