Bug 169025 Supports overridden on editor contribution
After contributting a new editor to the multiPageReportEditor, supports to enable the new editor to override a editor by assigning the ID.
UI/org.eclipse.birt.report.designer.ui.editors/src/org/eclipse/birt/report/designer/internal/ui/extension/EditorContributorManager.java
{
			FormPageDef element = (FormPageDef) iter.next( );
			if ( element.relative == null )
			{
				
				list.add( 0, element );
			}
			else
			{
				int relativePosition = getRelativeElementPosition( element,
						list );
				if ( relativePosition > -1 )
				{
					list.add( relativePosition + element.position, element );
					if ( relativeMap.containsKey( element ) )
					{
						
						List relativeList = (List) relativeMap.get( element );
						for ( Iterator iterator = relativeList.iterator( ); iterator.hasNext( ); )
						{
							FormPageDef relativeFormPage = (FormPageDef) iterator.next( );
							list.remove( relativeFormPage );
							list.add( relativePosition
									+ element.position
									+ relativeFormPage.position,
									relativeFormPage );
						}
					}
				}
				else