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 void removeExtension(IExtension extension, Object[] objects) {
		Collection removedGroups = new ArrayList();
		for (int i = 0; i < objects.length; i++) {
			if (objects[i] instanceof ProblemFilter) {
				registeredFilters.remove(objects[i]);
			}
			if (objects[i] instanceof MarkerGroup) {
				markerGroups.remove(((MarkerGroup) objects[i]).getId());
				removedGroups.add(objects[i]);
			}
			if (objects[i] instanceof MarkerGroupingEntry) {
				MarkerGroupingEntry entry = (MarkerGroupingEntry) objects[i];
				entry.getMarkerGroup().remove(entry);
				markerGroupingEntries.remove(entry.getId());
			}
			if (objects[i] instanceof String) {
				removeValues(objects[i], categories);
			}
		}
		Iterator entriesIterator = markerGroupingEntries.keySet().iterator();
		Collection removedKeys = new ArrayList();
		while (entriesIterator.hasNext()) {
			String entryId = (String) entriesIterator.next();
			MarkerGroupingEntry entry = (MarkerGroupingEntry) markerGroupingEntries
					.get(entryId);
			if (removedGroups.contains(entry.getMarkerGroup())) {
				removedKeys.add(entryId);
			}
		}