Bug 111885 [decorators] info if class or interface is in file
Currently the package explorer (and other widgets showing file lists) show a small 'J' icon for java files. It would be useful if this was one symbol for classes, and another for interfaces. The choice would be made based on the public class/interface in the file. I frequently have a class and interface of the same name in different packages, and it's hard to tell the difference.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/JavaPluginImages.java
* @param key the image's key
	 * @return the image descriptor for the given key
	 */ 
	public static ImageDescriptor getDescriptor(String key) {
		if (fgImageRegistry == null) {
			return (ImageDescriptor) fgAvoidSWTErrorMap.get(key);
		}
		return getImageRegistry().getDescriptor(key);
	}
	
	/**
	 * Sets the three image descriptors for enabled, disabled, and hovered to an action. The actions
	 * are retrieved from the *tool16 folders.
	 * 
	 * @param action	the action
	 * @param iconName	the icon name
	 */
	public static void setToolImageDescriptors(IAction action, String iconName) {
		setImageDescriptors(action, "tool16", iconName); 
	}
	
	/**
	 * Sets the three image descriptors for enabled, disabled, and hovered to an action. The actions
	 * are retrieved from the *lcl16 folders.
	 * 
	 * @param action	the action
	 * @param iconName	the icon name
	 */
	public static void setLocalImageDescriptors(IAction action, String iconName) {
		setImageDescriptors(action, "lcl16", iconName);