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
entryElement.setAttribute(ENTRY_ATTVALUE_VALUE, (String) entry.getValue());
				featureElement.appendChild(entryElement);
			}
		} else {
			featureElement.setAttribute(featureName, String.valueOf(value));
		}
		return featureElement;
	}
	private Element createUnsetDeltaElement(Document document, FeatureChange featureChange,
			String featureName) {
		Element featureElement = document.createElement(featureName);
		if (isChainedReference(featureName)) {
			appendOriginalReferenceElements(document, featureElement, (List<?>) featureChange
					.getValue());
		} else {
			featureElement.setAttribute(UNSET_ATTNAME, UNSET_ATTVALUE_TRUE);
		}
		return featureElement;
	}
	/**
	 * Creates an element to describe that the specified object was a reference that was originally
	 * there when the application started prior to the applying of any deltas. It should be noted
	 * that an object that was originally referenced will not necessarily be dereferenced after any
	 * deltas have been applied.
	 * 
	 * @param document
	 *            the root XML document
	 * @param reference
	 *            the referenced object
	 * @return an XML element to record that the specified object was originally referenced by