title: How to use FacetWP to search on category branches?
body: <p>I'm working on a website where I have posts that have multiple categories and subcategories assigned to them. Now I want to use FacetWP to give users the option to search these posts on their categories and subcategories. I want it to work hierarchical as the following example.</p>
  
  <p>Say one post has the following categories assigned to it:</p>
  
  <pre><code>France  - Paris   - River
                    - Street
          - Lyon    - Street
                    - House
  Germany - Hamburg - Street
          - Berlin  - House
                    - Church
  </code></pre>
  
  <p>Now I want to create dropdown facets, where I want the first dropdown to offer only the main categories (countries in this case). After that, when someone has selected a country, I want a second dropdown to only show the sub-categories of that particular country (cities in this case). After that, I want the next dropdown to only show the sub-sub-categories.</p>
  
  <p>So, when someone selects France, the next dropdown should only show Paris and Lyon (not Hamburg and Berlin). When Paris gets selected, the next dropdown should only show River and Street (not also House or Church)</p>
  
  <p>Is this possible with FacetWP? Or is there a way to tweak it to make it possible?</p>