Bug 188578 Add "displayColumnName" on TabularLevel
Add Property "displayColumnName" on TabbularLevel and corresponding APIs on handle. Property Type: expression.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/parser/TabularCubeParserTest.java
assertEquals( DesignChoiceConstants.ACCESS_PERMISSION_ALLOW,
				accessControl.getPermission( ) );
		propHandle = cube.getPropertyHandle( TabularCubeHandle.DIMENSIONS_PROP );
		assertEquals( 1, propHandle.getContentCount( ) );
		assertEquals( 1, cube
				.getContentCount( TabularCubeHandle.DIMENSIONS_PROP ) );
		
		iter = hierarchy.filtersIterator( );
		filterConditionHandle = (FilterConditionHandle) iter.next( );
		assertEquals( "filter expression", filterConditionHandle.getExpr( ) ); 
		List primaryKeys = hierarchy.getPrimaryKeys( );
		assertEquals( 3, primaryKeys.size( ) );
		assertEquals( "key", primaryKeys.get( 0 ) ); 
		assertEquals( "key2", primaryKeys.get( 1 ) ); 
		assertEquals( "key4", primaryKeys.get( 2 ) ); 
		propHandle = hierarchy
				.getPropertyHandle( TabularHierarchyHandle.LEVELS_PROP );
		assertEquals( 1, propHandle.getContentCount( ) );
		assertEquals( 1, hierarchy
				.getContentCount( TabularHierarchyHandle.LEVELS_PROP ) );
		
		TabularLevelHandle level = (TabularLevelHandle) propHandle
				.getContent( 0 );
		assertEquals( level, hierarchy.getContent(
				TabularHierarchyHandle.LEVELS_PROP, 0 ) );
		assertEquals( "testLevel", level.getName( ) ); 
		assertEquals( "column1", level.getColumnName( ) ); 
		assertEquals( DesignChoiceConstants.COLUMN_DATA_TYPE_INTEGER, level
				.getDataType( ) );
		assertEquals( "none", level.getInterval( ) );