Bug 124620 Referenced Parameter icon should be invalid if the parameter in library is deleted
Description: Referenced parameter icon should be invalid if the source parameter in library is deleted. Steps to reproduce: 1.Create a library. Insert a report scalar parameter. 2.Create a report, use the above library. In the library explorer, pull the parameter to the data explorer view of report. 3.Open the library file, delete the parameter. Then reopen the report design file, the icon of parameter seems nothing happened. But if those operations happened in dataset, the icon of dataset in the report will be invalid. It is acceptable. Expected Result: The icon of referenced parameter should be invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
* @throws SemanticException
	 *             If the property value cannot be converted from a double.
	 */
	public void setFloatProperty( String propName, double value )
			throws SemanticException
	{
		setProperty( propName, new Double( value ) );
	}
	/**
	 * Sets the value of a property to a number (BigDecimal).
	 * 
	 * @param propName
	 *            the property name
	 * @param value
	 *            the value to set
	 * @throws SemanticException
	 *             if the property value cannot be converted from a number.
	 */
	public void setNumberProperty( String propName, BigDecimal value )
			throws SemanticException
	{
		setProperty( propName, value );
	}
	/**
	 * Clears the value of a property. Clearing a property removes any value set
	 * for the property on this element. After this, the element will now
	 * inherit the property from its parent element, style, or from the default
	 * value for the property.
	 * 
	 * @param propName