title: Filtering <List> by custom parameter
body: <p>I am using <code>react-admin</code> (v3.2) and am trying to create a custom filter component. 
  My entities have an attribute <code>dateEnd</code> and I'd like to filter data based on if <code>dateEnd</code> is <code>expired</code> or <code>not expired</code>. I managed to get list of all entities: <code>expired</code> and <code>not expired</code>. </p>
  
  <p>However I don't know how can I display this list to a user.<br/>Is it possible by somehow creating the query in <code>URL</code>?</p>
  
  <p>This is my method that returns the list of <code>expired</code> and <code>not expired</code> entities:</p>
  
  <pre class="lang-js prettyprint-override"><code>handleChecked = () =&gt; {
    if(this._mounted) 
    {
       this.setState({ checked: !this.state.checked, currentDate: new Date()}, () =&gt;
         {
            const currentDateFormated = this.state.currentDate.toISOString();
            if (this.state.msgDates !== null)
            {
               if (this.state.checked === false)
               {
                  const notExpired = this.state.msgDates.filter(msg =&gt; get(msg, ["publish", "dateEnd"], []) &gt; currentDateFormated);
                          console.log(notExpired, 'NOTEXPIRED');
               }
               else
               {
                   const expired = this.state.msgDates.filter(msg =&gt; get(msg, ["publish", "dateEnd"], []) &lt; currentDateFormated);
                          console.log(expired, 'EXPIRED');
                }
             }
        });
     }
  }
  </code></pre>
  
  <p>And then I initialize my component in <code>Filter</code>:</p>
  
  <pre class="lang-js prettyprint-override"><code>const MessageFilter = (props) =&gt; (
     &lt;Filter {...props}&gt;
       &lt;TextInput source="_id" alwaysOn /&gt;
       &lt;TextInput source="layout.caption" alwaysOn /&gt;
       &lt;ExpiredFilter alwaysOn /&gt;
     &lt;/Filter&gt;
  );
  </code></pre>
  
  <p>Any ideas how can I show the list of expired or not expired entities? </p>
  
  <p>Thank you in advance.</p>