Bug 21013 [PropertiesView] ComboBoxPropertyDescriptor should provide a defualt label provider
ComboBoxPropertyDescriptor requires an array of string values in its contructor. These are used to display in the combo box cell editor. Typically clients must also supply a label provider with the same array of values in order to show the correct value when the cell editor is not active. The descriptor should create a default label provider based on the values passed in its constructor.
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertyDescriptor.java
* if none (the default).
	 */
	private ICellEditorValidator validator;
	/**
	 * Indicates if the descriptor is compatible with other descriptors of this
	 * type. <code>false</code> by default.
	 */
	private boolean incompatible = false;
/**
 * Creates a new property descriptor with the given id and display name
 */
public PropertyDescriptor(Object id, String displayName) {
	Assert.isNotNull(id);
	Assert.isNotNull(displayName);
	this.id = id;
	this.display = displayName;
}
/**
 * The <code>PropertyDescriptor</code> implementation of this 
 * <code>IPropertyDescriptor</code> method returns <code>null</code>.
 * <p>
 * Since no cell editor is returned, the property is read only.
 * </p>
 */
public CellEditor createPropertyEditor(Composite parent) {
	return null;
}
/**
 * Returns <code>true</code> if this property descriptor is to be always 
 * considered incompatible with any other property descriptor.