Bug 317954 Version deltas file so that incompatible changes will be ignored
The deltas file needs to be versioned so that incompatible changes will be discarded allowing the workbench to be constructed as if there were no deltas in existence.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/XMLModelReconciler.java
calculateDeltas();
		
		Document document = createDocument();
		Element root = document.createElement(CHANGES_ATTNAME);
		document.appendChild(root);
		EMap<EObject, EList<FeatureChange>> objectChanges = changeDescription.getObjectChanges();
		for (Entry<EObject, EList<FeatureChange>> entry : objectChanges.entrySet()) {
			EObject object = entry.getKey();
			
			Element persistedElement = persist(document, entry, object);
			if (persistedElement != null) {
				
				root.appendChild(persistedElement);
			}
		}
		return document;
	}
	/**
	 * Returns an XML representation of the changes that have occurred in the specified object. Or
	 * <code>null</code> if changes pertaining to this object should not be persisted
	 * 
	 * @param document
	 *            the root XML document
	 * @param entry
	 *            a list of changes that have occurred to the object
	 * @param object
	 *            the object to persist
	 * @return an XML representation of the changes of the object, or <code>null</code> if its
	 *         changes should be ignored
	 */