Bug 182780 [DataBinding] Default a converter for IStatus to String
The converter used to display an IStatus uses toString(). This outputs a fairly ugly status message. We should create a default converter and use this in UpdateValueStrategy to return just the message of the status.
bundles/org.eclipse.core.databinding/src/org/eclipse/core/databinding/AggregateValidationStatus.java
* Constant denoting an aggregation strategy that merges multiple non-OK
	 * status objects in a {@link MultiStatus}. Returns an OK status result if
	 * all statuses from the given bindings are the an OK status. Returns a
	 * single status if there is only one non-OK status.
	 * 
	 * @see #getStatusMerged(Collection)
	 */
	public static final int MERGED = 1;
	/**
	 * Constant denoting an aggregation strategy that always returns the most
	 * severe status from the given bindings. If there is more than one status
	 * at the same severity level, it picks the first one it encounters.
	 * 
	 * @see #getStatusMaxSeverity(Collection)
	 */
	public static final int MAX_SEVERITY = 2;
	/**
	 * @param bindings
	 *            an observable collection containing elements of type IStatus
	 * @param strategy
	 *            a strategy constant, one of {@link #MERGED} or
	 *            {@link #MAX_SEVERITY}.
	 */
	public AggregateValidationStatus(final IObservableCollection bindings,
			int strategy) {
		if (strategy == MERGED) {
			implementation = new ComputedValue() {
				protected Object calculate() {
					return getStatusMerged(bindings);
				}