make catchall bucket optional about graph-explorer

[Dieterbe]

thinking more about it, here's how i think aggregation and grouping should work:

• avg by & sum by:
  • no bucket specified -> aggregate all different values together
  • buckets -> aggregate only together what goes into same bucket (add catchall bucket if you want it)
  • catchall bucket -> aggregate different values together
  • -> no bucket specified defaults to a catchall bucket
• group by:
  • no bucket specified -> 1 group graph per every different value
  • buckets -> group what goes into same bucket onto 1 graph (add catchall bucket if you want it)
  • catchall bucket -> group different values on 1 graph.
  • -> no bucket specified defaults to no bucket

[Dieterbe]

until now, group by without explicit buckets defaults to catchall bucket and then uses that to make a graph per every different value which means we don't have a way to have a few buckets and a graph for all remaining items.

[Dieterbe]

here's some work in progress towards this https://github.com/vimeo/graph-explorer/tree/rethink-buckets