title: TypeError: datastore.getRootCollection is not a function
body: <p>I assumed a dstore that was created using dmodel was still a dstore and inherited all the dstore functionality.   So there's a method listed called getRootCollection but when i try to run this method on the store it fails with an error (no such function)</p>
  
  <p>Here is my code</p>
  
  <pre><code>&lt;script&gt;
  
      require(
          [
          'dojo/_base/declare',
          'dstore/Memory',
          'dmodel/extensions/jsonSchema',
          'dmodel/validators/StringValidator',
          'dmodel/store/Validating',
          "dmodel/Model"
          ], 
      function (declare, Memory, jsonSchema, StringValidator, Validating, Model) {
  
          var vMem = (declare([Memory, Validating]))({
              Model: jsonSchema(
              {
                  "$schema": "http://json-schema.org/draft-04/schema",
                  "description": "my schema",
                  "type": "object",
                  "properties": {
                      "page": {
                          "type": "object",
                          "properties": {
                              "detailsCanvas": {
                                  "description": "test value",
                                  "type": "object",
                                  "$ref": "#/definitions/details"
                              }
                          }
                      },
                      "elements": {
                          "type": "array",
                          "items": {
                              "title": "Element",
                              "type": "object",
                              "properties": {
                                  "id": {
                                      "type": "string"
                                  },
                                  "positionX": {
                                      "description": "The X coordinate",
                                      "type": "number"
                                  },
                                  "elementSpecificProperties": {
                                      "type": "object",
                                      "oneOf": [
                                        { "$ref": "#/definitions/label" }
                                      ]
                                  }
                              }
                          }
  
                      }
                  },
  
                  "definitions": {
  
                      "details": {
                          "type": "object",
                          "properties": {
                              "height": {
                                  "type": "string"
                              }
                          }
                      },
  
                      "label": {
                          "type": "object",
                          "properties": {
                              "value": {
                                  "type": "string"
  
                              }
                          }
                      }
                  }
              }
  
              )
          });
  
          vMem.setData(
          {
              "page": {
                  "detailsCanvas": {
                      "height": "100px"
                  }
              },
              "elements": [
                  {
                      "id": "1",
                      "positionX": 20,
                      "elementSpecificProperties": {
                          "value": "value_1"
                      }
                  },
                  {
                      "id": "2",
                      "positionX": 5,
                      "elementSpecificProperties": {
                          "value": "value_2"
                      }
                  }
              ]
          });
  
          var blah = vMem.getRootCollection(); //type error - getRootCollection is not a function
  
  
      });
  &lt;/script&gt;
  </code></pre>