Json export fix (#2043)

* Refactoring export to json to use new style objects

* Added convenience function to Object API to get identifiers as strings

* Updated tests for ExportAsJSON

* Fixed bug with parent composition not being updated with new ID. Also rewrite IDs in configuration etc. Fixes #2042

src/api/objects/ObjectAPI.js

@@ -207,6 +207,14 @@ define([
         return mutableObject.stopListening.bind(mutableObject);
     };
 
+    /**
+     * @param {module:openmct.ObjectAPI~Identifier} identifier
+     * @returns {string} A string representation of the given identifier, including namespace and key
+     */
+    ObjectAPI.prototype.makeKeyString = function (identifier) {
+        return utils.makeKeyString(identifier);
+    };
+
     /**
      * Uniquely identifies a domain object.
      *