Implement full user login with registration

...n/kotlin/de/thk/gm/gdw/todolist/configs/SecurityConfig.kt

...lin/de/thk/gm/gdw/todolist/controllers/TasksController.kt

...de/thk/gm/gdw/todolist/controllers/TasksRestController.kt

...lin/de/thk/gm/gdw/todolist/controllers/UsersController.kt

...de/thk/gm/gdw/todolist/controllers/UsersRestController.kt

...n/de/thk/gm/gdw/todolist/controllers/WelcomeController.kt

src/main/kotlin/de/thk/gm/gdw/todolist/dtos/UserDto.kt

src/main/resources/templates/index.ftlh

src/main/resources/templates/tasks/showTask.ftlh

src/main/resources/templates/users/dashboard.ftlh

src/main/resources/templates/users/showUsers.ftlh