Revamp faceted search for handling of multiple values per facet

[sashakames]

Current behavior assumes the following:

• best to automatically filter as you go

• user will select multiple values for a particular facet in one go and move on
  These aren't always desirable (no one size fits all)

• create a toggle for the automatic filter

• after a search, include a + option to add additional values from the original set of facet values instead of the filtered set