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/writer/DocumentUtilTest.java
{
	/**
	 * Design file name, which tests the element property value localization.
	 */
	private static final String DESIGN_WITH_ELEMENT_EXTENDS = "DocumentUtilTest.xml"; 
	/**
	 * Design file name, which tests the lib reference with library structures.
	 */
	private static final String DESIGN_WITH_STRUCTURE_REFERENCE = "DocumentUtilTest_1.xml"; 
	/**
	 * Design file name, which tests indirect element reference of library
	 * elements by inheritance.
	 */
	private static final String DESIGN_WITH_INDIRECT_REFERENCE = "DocumentUtilTest_2.xml"; 
	/**
	 * Design file name. Tests the shared style's name must not become element's
	 * name.
	 */
	private static final String DESIGN_WITH_SHARED_STYLE = "DocumentUtilTest_3.xml"; 
	/**
	 * Design file name.
	 */
	private static final String DESIGN_WITH_EXTERNAL_SELECTORS = "DocumentUtilTest_4.xml"; 
	/**
	 * Tests the element property value localization.
	 * 
	 * @throws Exception
	 */