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
* Return DesignElementHandle avaliable method's argument type name.
	 * 
	 * @param handle
	 *            DesignElementHandle.
	 * @param methodName
	 * @param argIdex
	 *            starts from 0.
	 * @return
	 */
	public static String getMethodArgumentType( DesignElementHandle handle,
			String methodName, int argIndex )
	{
		if ( handle instanceof DataSetHandle )
			return ReportDesignConstants.DATA_SET_ELEMENT; 
		if ( handle instanceof DataSourceHandle )
			return ReportDesignConstants.DATA_SOURCE_ELEMENT; 
		List methods = handle.getDefn( ).getLocalMethods( );
		for ( Iterator iter = methods.iterator( ); iter.hasNext( ); )
		{
			IMethodInfo method = ( (ElementPropertyDefn) iter.next( ) ).getMethodInfo( );
			if ( method.getName( ).equals( methodName ) )
			{
				Iterator argumentListIterator = method.argumentListIterator( );
				if ( argumentListIterator.hasNext( ) )
				{
					IArgumentInfoList argumentInfoList = (IArgumentInfoList) argumentListIterator.next( );
					int i = 0;
					for ( Iterator iterator = argumentInfoList.argumentsIterator( ); iterator.hasNext( ); i++ )
					{
						Object arg = iterator.next( );