Move logic from view into a helper: render_facet_limit_list

This doesn't read clearly to me. Do we need the double-map and compact, or can we just make this, e.g.:

```ruby
safe_join paginator.items.map { |item| content_tag(wrapping_element,  render_facet_item(solr_field, item)) }
```
Or, maybe, the wrapping element logic can be extracted (maybe such a helper already exists..):

```
wrap_each_with wrapping_element,  paginator.items.map { |item| render_facet_item(solr_field, item) }
```

Thoughts?