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
* Set up the fields and filters
	 */
	private void postProcessContentGenerators() {
		Iterator generatorIterator = generators.values().iterator();
		while (generatorIterator.hasNext()) {
			MarkerContentGenerator generator = (MarkerContentGenerator) generatorIterator
					.next();
			generator.initializeFromConfigurationElement(this);
		}
	}
	/**
	 * Process the grouping entries into thier required grouping entries.
	 * 
	 * @param groupingEntries
	 */
	private void processGroupingEntries(Map groupingEntries) {
		Iterator entriesIterator = groupingEntries.keySet().iterator();
		while (entriesIterator.hasNext()) {
			String nextGroupId = (String) entriesIterator.next();
			Iterator nextEntriesIterator = ((Collection) groupingEntries
					.get(nextGroupId)).iterator();
			if (markerGroups.containsKey(nextGroupId)) {
				while (nextEntriesIterator.hasNext()) {
					MarkerGroupingEntry next = (MarkerGroupingEntry) nextEntriesIterator
							.next();
					markerGroupingEntries.put(next.getId(), next);
					next.setGroupingEntry((MarkerGroup) markerGroups
							.get(nextGroupId));
				}
			} else {