implemented api to get all stations

src/main/java/hhn/labsw/bugageocaching/controller/Controller.java

@@ -195,4 +195,11 @@ public class Controller {
     return false;
   }
 
+  @CrossOrigin(origins = "http://localhost:8081") // only for dev purpose
+  @RequestMapping("/api/getAllStations")
+  @ResponseBody
+  String getAllStations() {
+    return new Gson().toJson(stationRepository.findAll());
+  }
+
 }