Bug 221521 [Markers] New markers API needs to be pared down
We have too much API in some of the new classes and they can be moved to internals
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/MarkerField.java
/**
	 * Compare item1 and item2 for sorting purposes.
	 * 
	 * @param item1
	 * @param item2
	 * @return Either:
	 *         <li>a negative number if the value of item1 is less than the
	 *         value of item2 for this field.
	 *         <li><code>0</code> if the value of item1 and the value of
	 *         item2 are equal for this field.
	 *         <li>a positive number if the value of item1 is greater than the
	 *         value of item2 for this field.
	 */
	public int compare(MarkerItem item1, MarkerItem item2) {
		return getValue(item1).compareTo(getValue(item2));
	}
	/**
	 * Generate the filter for the receiver from the configurationElement.
	 * 
	 * @return MarkerFieldFilter or <code>null</code>.
	 */
	public final MarkerFieldFilter generateFilter() {
		try {
			if (configurationElement.getAttribute(ATTRIBUTE_FILTER_CLASS) == null)
				return null;
			Object filter = IDEWorkbenchPlugin.createExtension(
					configurationElement, ATTRIBUTE_FILTER_CLASS);
			if (filter == null)
				return null;
			MarkerFieldFilter fieldFilter = (MarkerFieldFilter) filter;