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/internal/provisional/views/markers/MarkerContentGenerator.java
/**
	 * Return all of the filters for the receiver.
	 * 
	 * @return Collection of MarkerFieldFilterGroup
	 */
	public Collection getAllFilters() {
		if (filters == null) {
			filters = new ArrayList();
			IConfigurationElement[] filterReferences = configurationElement
					.getChildren(ELEMENT_MARKER_FIELD_FILTER_GROUP);
			for (int i = 0; i < filterReferences.length; i++) {
				filters.add(new MarkerFieldFilterGroup(filterReferences[i],
						this));
			}
			
			loadFiltersPreference();
		}
		return filters;
	}
	/**
	 * Return the group used to generate categories.
	 * 
	 * @return MarkerGroup or <code>null</code>.
	 */
	public MarkerGroup getCategoryGroup() {
		return categoryGroup;
	}
	/**
	 * Return a new instance of the receiver with the field
	 *