Bug 199834 Enable access to IContent object in IReportItemPresentation layer
In IReportItemPresentation layer, the extended item may want to access properties from current IContent object, for example, bookmark, content style. So we need expose the content object in this layer.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/QueryResultSet.java
return null;
		}
		/**
		 * Returns the column alias at the specified index. An alias is given to
		 * a column as a programmatic convenience. A column can be referred
		 * using a name or an alias interchangeably.
		 * 
		 * @param index
		 *            The projected column index.
		 * @return The alias of the specified column. Null if none is defined.
		 * @throws BirtException
		 *             if given index is invalid.
		 */
		public String getColumnAlias( int index ) throws BirtException
		{
			return null;
		}
		/**
		 * Returns the data type of the column at the specified index.
		 * 
		 * @param index
		 *            The projected column index.
		 * @return The data type of the specified column, as an integer defined
		 *         in org.eclipse.birt.data.engine.api.DataType.
		 * @throws BirtException
		 *             if given index is invalid.
		 */
		public int getColumnType( int index ) throws BirtException
		{
			return 0;