Bug 179737 The MeasureHandle should be able to provide data type info
We are now allow user input expression as measure expression. However this brings difficulties in determine the data type of a measure expression evaluation result. We need MeasureHandle to be enhanced to include the data type info. Please note that data type "any" is not accepted.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
* list tag.
	 * 
	 * @param obj
	 *            the container element
	 * @param slot
	 *            the slot to write
	 * @param tag
	 *            the optional list tag that encloses the list of contents
	 */
	protected void writeContents( DesignElement obj, int slot, String tag )
	{
		writeContents( new ContainerContext( obj, slot ), tag );
	}
	/**
	 * Writes the contents of an element property. The contents are enclosed in
	 * an optional list tag.
	 * 
	 * @param obj
	 *            the container element
	 * @param propName
	 *            the element property to write
	 * @param tag
	 *            the optional list tag that encloses the list of contents
	 */
	protected void writeContents( DesignElement obj, String propName )
	{
		writeContents( new ContainerContext( obj, propName ),
				DesignSchemaConstants.PROPERTY_TAG );
	}
	/**