#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

api/apps.py

@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class ApiConfig(AppConfig):
+    name = 'api'