Create Facet processors - Do not display items that do not narrow results

Problem/Motivation

We should port the "facet filters" from d7 facets + facet api bonus. We're renaming the "facet filters" to "facet processors" for more clarity on what the processors can do.

Remaining tasks

Create a new Processor that implements the \Drupal\facetapi\Processor\BuildProcessorInterface and hides all results that have a count that is equal to the current resultset but makes sure not to hide active items.

- this processor doesn't need a configuration form.