title: How to focus next input (if any) on next press
body: <p>I actually know how to this but I need a different approach.<br/>
  So I have text input like:</p>
  
  <pre><code>&lt;TextInput returnKeyType='next' 
             ref={ref =&gt; this.someName = ref}
             onSubmitEditing={(event) =&gt; { this.nextFieldName.focus() }}/&gt;
  </code></pre>
  
  <p>Trick is that I don't want to use specific name for next field but to simply focus next if any to focus.<br/>
  Is this possible?</p>