Bug 136571 Drop property is displayed in Property Editor for all kinds of cells.
Description: Drop property displayed in Property Editor for all kinds of cells. Drop property is only supported by cells in group but it is listed in every kinds of cells even in grid cell which will mislead users.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/SimpleGroupElementHandle.java
{
		List minProps = getMinPropDefns( );
		List commonProps = new ArrayList( minProps );
		Iterator iter = minProps.iterator( );
		while ( iter.hasNext( ) )
		{
			PropertyDefn propDefn = (PropertyDefn) iter.next( );
			for ( int i = 0; i < elements.size( ); i++ )
			{
				if ( !( (DesignElementHandle) elements.get( i ) ).getElement( )
						.getPropertyDefns( ).contains( propDefn ) )
				{
					commonProps.remove( propDefn );
					break;
				}
			}
		}
		return Collections.unmodifiableList( commonProps );
	}
	/**
	 * Returns the property definition list that has the minimum size.
	 * 
	 * @return the property definition list that has the minimum size.
	 */
	private List getMinPropDefns( )
	{
		int min = Integer.MAX_VALUE;
		List rtnPropDefns = Collections.EMPTY_LIST;
		for ( int j = 0; j < elements.size( ); j++ )
		{