Bug 221337 [Markers] MarkerItem has too much API
We are exposing too much as API in MarkerItem. We should only provide getAtttributeValue and the methods that support PATH_ATTRIBUTE and NAME_ATTRIBUTE as they are tricky. Everything else needs to be pushed down to an internal class. We should mention the relevant IMarker constants for those removed.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/MarkerField.java
*/
	public final int getSeverity(MarkerItem element) {
		if (element.isConcrete())
			return element.getAttributeValue(IMarker.SEVERITY, -1);
		return 0;
	}
	/**
	 * @param item
	 * @return The String value of the object for this particular field to be
	 *         displayed to the user.
	 */
	public abstract String getValue(MarkerItem item);
	/**
	 * Set the configuration element used by the receiver.
	 * 
	 * @param element
	 */
	public final void setConfigurationElement(IConfigurationElement element) {
		configurationElement = element;
	}
	/**
	 * Annotate the image with indicators for whether or not help or quick fix
	 * are available.
	 * 
	 * @param item
	 *            the item being decorated
	 * @param image
	 *            the image being overlaid
	 * @return Image
	 */