Bug 181365 There is no icon in the background image of MasterPage property editor
Description: In the property editor of Masterpage, go to advanced tab. Click Background node to set the "background image", but there is no icon to invoke the image resources in the local machine. In style builder, there is a "Browse.." button to set the background image. That will be more convient for user to set background image.
UI/org.eclipse.birt.report.designer.ui.views/src/org/eclipse/birt/report/designer/internal/ui/views/attributes/provider/GroupPropertyHandleProvider.java
{
		if ( o instanceof GroupPropertyHandle )
		{
			return ( (GroupPropertyHandle) o ).isReadOnly( );
		}
		return false;
	}
	/**
	 * Determines whether this is a visible property.
	 * 
	 * @param o
	 *            the property model to inspect
	 * @return true if a visible property
	 */
	public boolean isEditable( Object o )
	{
		if ( o instanceof GroupPropertyHandle )
		{
			return ( (GroupPropertyHandle) o ).getPropertyDefn( ).isEditable( );
		}
		return false;
	}
	/**
	 * Get the value's position in the choice list it belongs to.
	 * 
	 * @param o
	 *            the property model to inspect
	 * @param value
	 *            the specified value
	 * @return the position