Bug 214649 [Markers] Allow markerAttributeGroupings and markerGroups to be specified within contentGenerators
With everything at the top level it is hard to see the relation to a contentGenerator and the groups and attribute groupings. These should be sub elements a la menus.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/CachedMarkerBuilder.java
* @param start
	 *            the start index in the markers
	 * @param end
	 *            the last index to check
	 * @param sortIndex -
	 *            the parent of the field
	 * @return MarkerCategory[] or <code>null</code> if we are at the bottom
	 *         of the tree
	 */
	MarkerCategory[] buildHierarchy(MarkerMap markers, int start, int end,
			int sortIndex) {
		MarkerComparator sorter = getComparator();
		if (sortIndex > 0) {
			return null;
		}
		Collection categories = new ArrayList();
		Object previous = null;
		int categoryStart = start;
		Object[] elements = markers.toArray();
		for (int i = start; i <= end; i++) {
			if (previous != null) {
				
				if (sorter.compareCategory(previous, elements[i]) != 0) {
					categories
							.add(new MarkerCategory(
									this,
									categoryStart,
									i - 1,
									getCategoryGroup()
											.getMarkerField()