add new property of Application model for oauth2.0 grant type

* "grantType": ["string"]

 Array of 'grantType' property has to be one more of the followings.
 - authorization_code, implicit, password, client_credentials

common/models/application.json

@@ -30,6 +30,10 @@
     "email": "string",
     "emailVerified": "boolean",
 
+    "grantType": {
+      "type": ["string"],
+      "description": "Grant type permitted to the application for OAuth 2.0"
+    },
     "url": {
       "type": "string",
       "description": "The application URL for OAuth 2.0"