Renamed `WindowEventsPoller::CallWindowEvent` to `callWindowEventHandler`;
In `WindowEventsPoller`:
  `container_type` and `windows_container` are now private;
Added private methods to `WindowEventsPoller`:
  - `isWindowExpired(id)`
  - `unregisterWindow(id)`
  - `callSpecifiedWindowEventHandler(event, window)`
Umm... definitions;
If window called by `callWindowEventHandler` is expired then its just unregistered, and nothing happends.