title: Add Property to ControlsFX PropertySheet
body: <p>I am creating a <code>PropertySheet</code> and I want to add a <code>Property</code> to the sheet. The problem is, what happens if the value of the property changes, the <code>PropertySheet</code> needs to update to reflect those changes. How would I do this?</p>
  
  <pre><code>import java.util.Map;
  
  import javafx.beans.property.Property;
  
  import org.controlsfx.control.PropertySheet;
  
  public class PropertyItem implements PropertySheet.Item {
      private Map&lt;String, Property&gt; map;
      private String key;
      private String name;
      private String description;
  
      PropertyItem(Map&lt;String, Property&gt; map, String key, String name, String description){
          this.map = map;
          this.key = key;
          this.name = name;
          this.description = description;
      }
      @Override
      public String getCategory() {
          return null;
      }
  
      @Override
      public String getDescription() {
          return description;
      }
  
      @Override
      public String getName() {
          return name;
      }
  
      @Override
      public Class&lt;?&gt; getType() {
          return map.get(key).getValue().getClass();
      }
  
      @Override
      public Object getValue() {
          return map.get(key).getValue();
      }
  
      @Override
      public void setValue(Object arg0) {
          map.get(key).setValue(arg0);
      }
  }
  </code></pre>