Bug 122854 There is redundant columns in "available columns" list in "export data" dialog.
Description: There is redundant columns in "available columns" list in "export data" dialog. Steps to reproduce: 1. Preview attached design in web viewer. 2. Select the table and click on "export" button. 3. There is a "detail" column name in "available columns" list which is not data set column.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/ir/Report.java
* get the report's page setup
	 * 
	 * @return page setup of this report
	 */
	public PageSetupDesign getPageSetup( )
	{
		return this.pageSetup;
	}
	/**
	 * get total contents.
	 * 
	 * @return sections in the report body.
	 */
	public ArrayList getContents( )
	{
		return this.contents;
	}
	/**
	 * get contents count in a report.
	 * 
	 * @return content count
	 */
	public int getContentCount( )
	{
		return this.contents.size( );
	}
	/**
	 * get content at index.
	 * 
	 * @param index