#31 API basic implementation

* adds new app to project
* adds relation between User model and new APIUserToken model
* adds first implementation for GET of intervention
* adds basic code layout for future extension by having new versions

konova/sub_settings/django_settings.py

@@ -70,6 +70,7 @@ INSTALLED_APPS = [
     'ema',
     'codelist',
     'analysis',
+    'api',
 ]
 if DEBUG:
     INSTALLED_APPS += [