Bug 151959 inappropriate screen operation
steps to reproduce: - create a report - add a grid item (3x3) - switch to Outline view - expand the grid item to see its rows and cells - select the grid item, and drag it into any of its own cell expected behavior: - is it an invalid screen operation? if it is, it should be banned actual behavior: - the grid item was disappeared surprisingly
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* "ElementType('Name')". Otherwise, locate the first container with name
	 * and generate the containment path with the form,
	 * "Container.Slot[Position]". If no container has name defined, "report" or
	 * container element type will be used as container's identifier, depending
	 * on whether this element is added into one report design.
	 * <p>
	 * For example,
	 * <ul>
	 * <li>report.body[0] - The first element in body slot
	 * <li>table("myTable") - The table named myTable
	 * <li>table("myTable").detail[0].cells[3] - The forth cell of the first
	 * row in table
	 * </ul>
	 * <p>
	 * Note: the localized name is used for element type and slot name.
	 * 
	 * @return the identifier of this element
	 */
	public String getIdentifier( )
	{
		if ( getName( ) != null )
		{
			StringBuffer sb = new StringBuffer( );
			sb.append( getDefn( ).getDisplayName( ) );
			sb.append( "(\"" ); 
			sb.append( getName( ) );
			sb.append( "\")" ); 
			return sb.toString( );
		}
		if ( this instanceof ReportDesign )