Add repositories

- Make model classes imutable
- Move model classes to common module
- Add repositories for backend and frontend
  - Backend repositories communicates with sqlite
  - Frontend repositories commuincates with rest api
- Add rest api
  - Authentication via cookies
- Add coroutines to forntend
- Add change listener to repositories
- Transmit change events to frontend repositories via websocket
- Switch to server side sessions
- Move setup from ui to cli

src/jvmTest/resources/test.http

@@ -0,0 +1,38 @@
+GET http://localhost:8080/api/rooms
+
+###
+
+POST http://localhost:8080/api/authenticate
+Content-Type: application/json
+
+{
+  "username": "admin",
+  "password": "admin"
+}
+
+
+> {%
+ client.assert(response.body.OK === true, "Login failed!");
+ client.global.set("auth_token", response.headers.valueOf("Set-Cookie"));
+ %}
+
+###
+
+POST http://localhost:8080/api/rooms
+Content-Type: application/json
+Cookie: {{auth_token}}
+
+{
+  "name": "E007",
+  "places": 20,
+  "projector": true
+}
+
+###
+
+
+POST http://localhost:8080/api/room/2/delete
+Content-Type: application/json
+Cookie: {{auth_token}}
+
+###