[feature] Add explicitly-created document property.

Author: chris-evolvedbinary

exist-core/src/main/java/org/exist/dom/memtree/DocumentImpl.java

@@ -211,6 +211,10 @@ public long getDocId() {
         return docId;
     }
 
+    public boolean isExplicitlyCreated() {
+        return explicitlyCreated;
+    }
+
     public int addNode(final short kind, final short level, final QName qname) {
         if(nodeKind == null) {
             init();