Bug 218884 [DataBinding] Add API: WorkbenchObservables
... for things like listening to ISelectionService
bundles/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/Observables.java
*            the key identifying the map entry to track.
	 * @param valueType
	 *            the type of the value. May be <code>null</code>, meaning
	 *            the value is untyped.
	 * @return an observable value that tracks the value associated with the
	 *         specified key in the given map
	 * @since 1.1
	 */
	public static IObservableValue observeMapEntry(IObservableMap map,
			Object key, Object valueType) {
		if (valueType == null)
			valueType = map.getValueType();
		return new MapEntryObservableValue(map, key, valueType);
	}
	/**
	 * Returns a factory for creating obervable values tracking the value of the
	 * {@link IObservableMap observable map} entry identified by a particular
	 * key.
	 * 
	 * @param map
	 *            the observable map whose entry will be tracked.
	 * @param valueType
	 *            the type of the value. May be <code>null</code>, meaning
	 *            the value is untyped.
	 * @return a factory for creating observable values tracking the value of
	 *         the observable map entry identified by a particular key object.
	 * @since 1.1
	 */
	public static IObservableFactory mapEntryValueFactory(
			final IObservableMap map, final Object valueType) {