Bug 139110 GUI enhancement to support create subquery more conveniently.
Description: GUI enhancement to support create subquery more conveniently. Steps to reproduce: Subquery means insert table/list inside another table/list item, and the inner table/list item doesn't has its own dataset binding. In latest build, if you want to creat a subquery structure, you have to use dataSetRow as binding expression for data items in inner table/list item. For example: 1. Insert a list, generate column data binding for it. 2. Add a group for the list. 3. Insert table to list group header which is used to display data rows in list group. Dont' bind table to dataset. 4. Insert a data to table detail row. 5. New a binding column for data, click to Open Expression Builder. The issue is that only "Availabel column bindings" is listed in Category but no "Available Data Sets". So I have to type dataSetRow[".."] by myself to generate correct subquery. For users, maybe they will mistakenly use "Available column bindings" which will generate expression like row._outer[".."] and get wrong result. So it is recommended to add "Available Data Sets" in Expression Builder for such case.
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
* @param obj
	 */
	public static String getDisplayLabel( Object obj )
	{
		return getDisplayLabel( obj, true );
	}
	/**
	 * Get display label of report element
	 * 
	 * @param obj
	 */
	public static String getDisplayLabel( Object obj, boolean includeElementName )
	{
		if ( obj instanceof DesignElementHandle )
		{
			DesignElementHandle handle = (DesignElementHandle) obj;
			String elementName = handle.getDefn( ).getDisplayName( );
			String displayName;
			if ( handle.getQualifiedName( ) != null
					&& !handle.getQualifiedName( ).equals( handle.getName( ) ) )
			{
				displayName = handle.getQualifiedName( );
			}
			else
			{
				displayName = handle.getDisplayLabel( DesignElementHandle.USER_LABEL );
			}
			if ( !StringUtil.isBlank( displayName ) )
			{
				if ( includeElementName )