EcoreUtil2: Introduce getAllContentsOfType() for resources

EcoreUtil2 already contains several methods that come in two variants,
one for EObjects and one for Resources. getAllContentsOfType() lacks a
Resource variant, so introduce it to simplify Resource querying.

org.eclipse.xtext/src/org/eclipse/xtext/EcoreUtil2.java

@@ -189,6 +189,10 @@ public static <T extends EObject> List<T> getAllContentsOfType(EObject ele, Clas
 		return Lists.newArrayList(Iterators.filter(ele.eAllContents(), type));
 	}
 
+	public static <T extends EObject> List<T> getAllContentsOfType(Resource resource, Class<T> type) {
+		return Lists.newArrayList(Iterators.filter(resource.getAllContents(), type));
+	}
+
 	public static <T> List<T> typeSelect(List<?> elements, Class<T> clazz) {
 		return Lists.newArrayList(Iterables.filter(elements, clazz));
 	}