Bug 208055 [Markers] Need a sorting method for the markers view
As there is currently no accessible way to change sort order or direction. A menu should be enough.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/MarkerContentGenerator.java
* @return MarkerGroup or <code>null</code>.
	 */
	public MarkerGroup getCategoryGroup() {
		return categoryGroup;
	}
	/**
	 * Return a new instance of the receiver with the field
	 * 
	 * @return MarkerComparator
	 */
	public MarkerComparator getComparator() {
		if (comparator == null) {
			MarkerField field = null;
			if (getCategoryGroup() != null)
				field = getCategoryGroup().getMarkerField();
			comparator = new MarkerComparator(field, getAllFields());
			comparator.restore(this.memento);
		}
		return comparator;
	}
	/**
	 * Return the currently enabled filters.
	 * 
	 * @return Collection of MarkerFieldFilterGroup
	 */
	public Collection getEnabledFilters() {
		if (enabledFilters == null) {
			enabledFilters = new HashSet();
			Iterator filtersIterator = getAllFilters().iterator();
			while (filtersIterator.hasNext()) {