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/dnd/InsertInLayoutUtil.java
{
					return false;
				}
			}
			return true;
		}
		else if ( insertObj instanceof IStructuredSelection )
		{
			return handleValidateInsertToLayout( ( (IStructuredSelection) insertObj ).toArray( ),
					targetPart );
		}
		else if ( insertObj instanceof DataSetHandle )
		{
			return isHandleValid( (DataSetHandle) insertObj )
					&& handleValidateDataSet( targetPart );
		}
		else if ( insertObj instanceof ResultSetColumnHandle )
		{
			return handleValidateDataSetColumn( (ResultSetColumnHandle) insertObj,
					targetPart );
		}
		else if ( insertObj instanceof ScalarParameterHandle )
		{
			return isHandleValid( (ScalarParameterHandle) insertObj )
					&& handleValidateParameter( targetPart );
		}
		return false;
	}
	private static boolean checkContainContainMulitItem( Object[] objects,
			Object slotHandle )