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
}
	private static int getElementPosition( FormPageDef relativeElement,
			List list )
	{
		return list.indexOf( relativeElement );
	}
	private static void addRelativeMap( FormPageDef element, List formPageList,
			Map relativeMap )
	{
		for ( Iterator iter = formPageList.iterator( ); iter.hasNext( ); )
		{
			FormPageDef formPage = (FormPageDef) iter.next( );
			if ( formPage.id.equals( element.relative ) )
			{
				if ( relativeMap.containsKey( formPage ) )
				{
					( (ArrayList) relativeMap.get( formPage ) ).add( element );
				}
				else
				{
					ArrayList list = new ArrayList( );
					list.add( element );
					relativeMap.put( formPage, list );
				}
				break;
			}
		}
	}
	private static int getRelativeElementPosition( FormPageDef element,
			List list )