Bug 174872 Clean up chart model
The chart model contains unused attributes and components. Those just make it difficult to understand the model architecture, so they should be removed from the schema, and the EMF classes must re-generated. Examples are: ChartPreferences, Rule. We need to analyze the model to find out all unused ones. Note that this should not break backward compatibility, otherwise just make them deprecated.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/data/DataFactory.java
* @generated
	 */
	GanttDataSet createGanttDataSet( );
	/**
	 * Returns a new object of class '<em>Number Data Element</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Number Data Element</em>'.
	 * @generated
	 */
	NumberDataElement createNumberDataElement( );
	/**
	 * Returns a new object of class '<em>Number Data Set</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Number Data Set</em>'.
	 * @generated
	 */
	NumberDataSet createNumberDataSet( );
	/**
	 * Returns a new object of class '<em>Orthogonal Sample Data</em>'. <!-- begin-user-doc --> <!-- end-user-doc
	 * -->
	 * 
	 * @return a new object of class '<em>Orthogonal Sample Data</em>'.
	 * @generated
	 */
	OrthogonalSampleData createOrthogonalSampleData( );
	/**
	 * Returns a new object of class '<em>Query</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Query</em>'.
	 * @generated