Bug 160429 Drag the datasource and dataset and produce an error gradation in data explorer
Details: Drag the datasource and dataset and produce an error gradation in data explorer Step: 1.New 4 datasource named d1, d2, d3, d4. 2.Drag the datasource in data explorer to change the gradation. (1) Drag d1 between d2 and d3. (2) Drag d2 between d3 and d4. (3) Drag d4 between d2 and d3. (4) Drag d4 to the top. (5) Drag d3 between d1 and d2. (6) Drag d3 to the top. Actual result: (1) d1 will be move to bottom. (2) d2 will be move to bottom. (3) d4 will not be move to anywhere. (4) d4 will not be move to anywhere. (5) d3 will be move to bottom. (6) d3 will be move to bottom. Excepted result: The datasource will be move to the correct station.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ModuleHandle.java
tempList = library.getNativeStructureList( propName );
			if ( !tempList.isEmpty( ) )
				list.addAll( tempList );
		}
		return list;
	}
	/**
	 * Returns the structures which are defined locally in the current module.
	 * This method will collect all structures from the current module file
	 * locally.
	 * 
	 * @param propName
	 *            name of the list property
	 * @return the structure list, each of which is the instance of
	 *         <code>StructureHandle</code>
	 */
	List getNativeStructureList( String propName )
	{
		List list = new ArrayList( );
		PropertyHandle propHandle = getPropertyHandle( propName );
		assert propHandle != null;
		Iterator iter = propHandle.iterator( );
		while ( iter.hasNext( ) )
		{
			StructureHandle s = (StructureHandle) iter.next( );
			list.add( s );
		}
		return list;
	}
	/**