feat: commit a filter as a named slice

[willeppy]

Save the current filters into a named slice. Can then also see all the columns derived from that slice. This requires several new features probably, I think:

1. Save current selections as a named slice
2. Ability to re-load slices into current selection from a list or drop down
3. When new column created, affiliate it with a slice (either make new or associate with the current slice)
4. For derived columns, ability to load their originating slice into the current selection from the column profiles

[willeppy]

I think the second feature (re-loading slices into current selection) is important to make this actually usable but is not possible with mosaic currently. Because you need a way to populate selections with pre-existing selections that have been saved to the database.

In future, if move away from mosaic this will be easier and more feasible