Bug 205049 Other plug-ins should be able to define default content generator
Currently only the content generator can define which plug-ins it can be the default for - we need a way for plug-ins to refer back to the marker support for thier own generator.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerSupportRegistry.java
public String getCategory(String markerType) {
		if (categories.containsKey(markerType)) {
			return (String) categories.get(markerType);
		}
		return null;
	}
	/**
	 * Return the TableSorter that corresponds to type.
	 * 
	 * @param type
	 * @return TableSorter
	 */
	public TableComparator getSorterFor(String type) {
		if (hierarchyOrders.containsKey(type)) {
			return (TableComparator) hierarchyOrders.get(type);
		}
		TableComparator sorter = findSorterInChildren(type, getRootType());
		if (sorter == null) {
			return new TableComparator(new IField[0], new int[0], new int[0]);
		}
		return sorter;
	}
	/**
	 * Return the list of root marker types.
	 * 
	 * @return List of MarkerType.
	 */
	private MarkerType getRootType() {
		if (rootType == null) {
			rootType = (MarkerTypesModel.getInstance())