Support views with more than one date filter

The module ships two date cache plugins. One caches archive views (a single "less than" date filter) and the other caches upcoming views (a single "greater than" filter). Each one only looks at a single filter.

That leaves out any view bounded by two date filters at once. The common example is a "currently running" view, where an item should show while now sits between its start and end. On a daterange field that is a "less than"
filter on the start column and a "greater than" filter on the end column, two filters working together. There is no way to cache that today, and no single plugin lets you combine a "less than" and a "greater than" filter.

This issue is to let the caching key off more than one date filter and expire at the soonest moment any of them next changes the result set.