title: How to remove icons from the BottomNavigationBar?
body: <p>I just need the the label in my BottomNavigationBarItem's but I cant find a way to remove them.<br>
  You can hide the labels with <code>showSelectedLabels</code> and <code>showUnselectedLabels</code> set to false but there are no equivalent for Icons.</p>
  
  <p>Constructor:</p>
  
  <pre><code>BottomNavigationBar({
      Key key,
      @required this.items,
      this.onTap,
      this.currentIndex = 0,
      this.elevation = 8.0,
      BottomNavigationBarType type,
      Color fixedColor,
      this.backgroundColor,
      this.iconSize = 24.0,
      Color selectedItemColor,
      this.unselectedItemColor,
      this.selectedIconTheme = const IconThemeData(),
      this.unselectedIconTheme = const IconThemeData(),
      this.selectedFontSize = 14.0,
      this.unselectedFontSize = 12.0,
      this.selectedLabelStyle,
      this.unselectedLabelStyle,
      this.showSelectedLabels = true,
      bool showUnselectedLabels,
    })
  </code></pre>