Add -H (humanize) for con-duct ls

What we have
```
con-duct ls -F wall_clock_time
- prefix: <irrelevant>
  wall_clock_time: 1534.373 sec
```

What would be nice

```
con-duct ls -H -F wall_clock_time
- prefix: <irrelevant>
  wall_clock_time: 25m 34.4s
```

It might be worth accepting -H/--humanize at the highest level like --log-level and using it wherever