Implement enhanced query stats/summary

Create a summary for each processing phase. Something like:
```
read: 316.0 M records (containing 5.2 G packets, 5.8 T bytes), took 43.952477 seconds, 7.2 M flows/second
input filter: 15.0 M records (containing 1.2 G packets, 1.8 T bytes), took 43.952477 seconds, 341.4 k flows/second
aggregation: 1990 records ...
sorting: ...
output filter: ...
```