include the standard deviation of "inbreeding" measurements (dragoon/komodo!119)

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