Bug 179737 The MeasureHandle should be able to provide data type info
We are now allow user input expression as measure expression. However this brings difficulties in determine the data type of a measure expression evaluation result. We need MeasureHandle to be enhanced to include the data type info. Please note that data type "any" is not accepted.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
* 
	 * @param obj
	 *            the design element to write
	 * @param propName
	 *            the name of the structure list property to write
	 */
	protected void writeStructureList( DesignElement obj, String propName )
	{
		PropertyDefn prop = (ElementPropertyDefn) obj.getDefn( ).getProperty(
				propName );
		assert prop != null;
		assert prop.getTypeCode( ) == IPropertyType.STRUCT_TYPE
				&& prop.isList( );
		List list = (List) obj.getLocalProperty( getModule( ), propName );
		if ( list == null || list.size( ) == 0 )
			return;
		writer.startElement( DesignSchemaConstants.LIST_PROPERTY_TAG );
		writer.attribute( DesignSchemaConstants.NAME_ATTRIB, propName );
		Iterator iter = list.iterator( );
		while ( iter.hasNext( ) )
		{
			IStructure struct = (IStructure) iter.next( );
			writer.startElement( DesignSchemaConstants.STRUCTURE_TAG );
			if ( struct instanceof IncludedLibrary )
				markLineNumber( struct );
			Iterator memberIter = prop.getStructDefn( ).propertiesIterator( );
			while ( memberIter.hasNext( ) )
			{
				PropertyDefn memberDefn = (PropertyDefn) memberIter.next( );