title: How to add icons to PreferenceScreen entries
body: <p>Consider this preferences.xml file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:title="@string/preference_main"&gt;
      &lt;PreferenceScreen
          android:title="@string/preference_sight"
          android:key="category_sight"&gt;
          &lt;ListPreference 
              android:summary="@string/preference_sight_wb_msg"
              android:title="@string/preference_sight_wb_title"
              android:key="sight_wb" android:defaultValue="auto"/&gt;
          &lt;Preference
              android:key="sight_wb_values_cache"/&gt;
          &lt;eu.elevelcbt.sm.preferences.PercentBarPreference
              android:title="@string/preference_sight_mean_confidence_min_title"
              android:summary="@string/preference_sight_mean_confidence_min_msg"
              android:key="sight_mean_confidence_min"
              android:defaultValue="80"/&gt;
          &lt;CheckBoxPreference 
              android:key="sight_flash"
              android:defaultValue="false"
              android:summary="@string/preference_sight_flash_msg"
              android:title="@string/preference_sight_flash_title"/&gt;
      &lt;/PreferenceScreen&gt;
  &lt;/PreferenceScreen&gt;
  </code></pre>
  
  <p>When shown in my MainPreference class extending PreferenceActivity is correctly shows me a first level menu with one entry "Sight" (@string/preference_main) which, when selected, takes me to the second preference screen where I have all my preferences. Everything works as I wanted. The only thing is the on first preference screen I want to put an icon beside the label "Sight" like in main Android setting menu.</p>
  
  <p>How can I do that? Thank you very much in advance for any help!
  Luca.</p>
  
  <p>Mine:
  <img src="https://i.stack.imgur.com/WrOyL.png" alt="Mine"></p>
  
  <p>Desired:
  <img src="https://i.stack.imgur.com/zwBni.png" alt="Desired"></p>
  
  <hr>
  
  <p>...mmm I tried but no luck...</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:title="@string/preference_main"&gt;
    &lt;PreferenceScreen
          android:title="@string/preference_sight"
          android:key="category_sight"
          android:icon="@drawable/ic_dialog_light"&gt;
  ...
  &lt;/PreferenceScreen&gt;
  </code></pre>
  
  <p>where am I doing wrong?</p>