Bug 127289 [Markers] SystemFilter and group selection state not preserved
We are not preserving the selection state of the system filters or which group is selected.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/CategorySorter.java
IField categoryField;
	private final String TAG_FIELD = "categoryField"; 
	/**
	 * Create a new instance of the receiver wrapping a sorter.
	 * 
	 * @param sorter
	 */
	CategorySorter(TableSorter sorter) {
		innerSorter = sorter;
	}
	/**
	 * Compare obj1 and obj starting with field depth.
	 * 
	 * @param obj1
	 * @param obj2
	 * @param depth
	 * @param continueSearching
	 * @return int
	 * @see ViewerSorter#compare(Viewer, Object, Object)
	 */
	int compare(Object obj1, Object obj2, int depth, boolean continueSearching) {
		if (obj1 == null || obj2 == null || !(obj1 instanceof MarkerNode)
				|| !(obj2 instanceof MarkerNode)) {
			return 0;
		}
		MarkerNode marker1;
		MarkerNode marker2;
		marker1 = (MarkerNode) obj1;
		marker2 = (MarkerNode) obj2;
		if (categoryField == null) {