Bug 119550 Default Value of Named Expression can't be saved in design file
New a report, set named expression in the report property editor add a named expression and set the default value add a report item, say table, to the layout set the named expression of the report item add a named expression and set hte default value save the report close the report and reopen, and there is no default named expression value displayed. open report design file with a text editor, there is no default value associate with the named expression
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/core/UserPropertyDefn.java
* of <code>IPropertyType</code>.
	 * 
	 * @return the list of allowed property types for user property.
	 */
	public static List getAllowedTypes( )
	{
		if ( allowedTypes != null )
			return allowedTypes;
		allowedTypes = new ArrayList( );
		Iterator iter = MetaDataDictionary.getInstance( ).getPropertyTypes( )
				.iterator( );
		while ( iter.hasNext( ) )
		{
			PropertyType propType = (PropertyType) iter.next( );
			int type = propType.getTypeCode( );
			switch ( type )
			{
				case PropertyType.STRUCT_TYPE :
				case PropertyType.STRUCT_REF_TYPE :
				case PropertyType.ELEMENT_REF_TYPE :
				case PropertyType.EXTENDS_TYPE :
					break;
				default :
					allowedTypes.add( propType );
			}
		}
		return allowedTypes;
	}
	/**
	 * Gets the value of property by the given property definition.