allow incoming KaleidoscopeEvent to specify create date

Allow the specification of the KaleidoscopeEvent creation date/time.
This allows Sites and Venue to emit their recent history to a Core when
connecting to populate the Core with their content upon arrival.

app/services/hive.js

@@ -206,8 +206,16 @@ class HiveService extends SiteService {
       throw new SiteError(406, 'Missing source emitter href');
     }
 
+    /*
+     * Create the KaleidoscopeEvent document
+     */
+
     const event = new KaleidoscopeEvent();
-    event.created = NOW;
+    if (eventDefinition.created) {
+      event.created = new Date(eventDefinition.created);
+    } else {
+      event.created = NOW;
+    }
 
     if (eventDefinition.recipientType && eventDefinition.recipient) {
       event.recipientType = eventDefinition.recipientType;