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 IReportElementConstants.PARAMETER_PREFIX
					+ "[\"" + escape( ( (ParameterHandle) model ).getQualifiedName( ) ) + "\"]"; 
		}
		if ( model instanceof DataSetItemModel )
		{
			String colName = ( (DataSetItemModel) model ).getAlias( );
			if ( colName == null || colName.trim( ).length( ) == 0 )
			{
				colName = ( (DataSetItemModel) model ).getName( );
			}
			return getColumnExpression( colName );
		}
		if ( model instanceof ComputedColumnHandle )
		{
			return getColumnExpression( ( (ComputedColumnHandle) model ).getName( ) );
		}
		if ( model instanceof ResultSetColumnHandle )
		{
			return getResultSetColumnExpression( ( (ResultSetColumnHandle) model ).getColumnName( ) );
		}
		return null;
	}
	/**
	 * Returns the integer font size for string value.
	 * 
	 * @param fontSize
	 * @return
	 */
	public static int getFontSize( String fontSize )