Bug 166015 Refactor designer actions to eclipse command framework
Eclipse command framework provide a more explicit way to manage UI actions contributions, we can take it's advantage to make our actions code more clean and maintainable.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/editors/schematic/actions/SplitAction.java
* (non-Javadoc)
	 * 
	 * @see org.eclipse.gef.ui.actions.WorkbenchPartAction#calculateEnabled()
	 */
	protected boolean calculateEnabled( )
	{
		if ( getRowHandles( ).isEmpty( ) && getColumnHandles( ).isEmpty( ) )
		{
			return getTableEditPart( ) != null && cellCanSplit( );
		}
		return false;
	}
	/**
	 * Determines whether selected cell can be splited.
	 * 
	 * @return
	 */
	private boolean cellCanSplit( )
	{
		if ( getSelectedObjects( ).size( ) != 1 )
		{
			return false;
		}
		Object obj = getSelectedObjects( ).get( 0 );
		if ( obj instanceof TableCellEditPart )
		{
			CellHandleAdapter adapt = HandleAdapterFactory.getInstance( )
					.getCellHandleAdapter( ( (TableCellEditPart) obj ).getModel( ) );
			if ( adapt.getRowSpan( ) != 1 || adapt.getColumnSpan( ) != 1 )
			{