Overrided `Window::pollEvent`
Added empty definition of `SDL2Window::pollEvent` method
Added `SDL2WindowEventsPoller` header with:
  - class `SDL2WindowEventsPoller` extending `WindowEventsPoller`, which:
      - overrides `pollEvents` method
There is no `pollEvent` method!;
Added definition of `SDL2Window::ID` method
There is no `pollEvent` method!
Added `SDL2WindowEventsPoller` source file with empty `SDL2WIndowEventsPoller::pollEvents` method
In `SDL2WindowEventsPoller::pollEvents`:
  - added Polling loop
Added `SDL2WindowEvents` header with:
  - `SDL2WindowEvent` extending WindowEvent with:
    - constructor :)
Added `SDL2WindowEvents` source file and empty `SDL2WIndowEvent` constructor
Included `map` header
In `SDL2WIndowEvent` constructor:
  - create static map with both SDL and vulture event types
  - if event was found in map, set a type
in `SDL2WindowEventsPoller` method:
  - create sdl_event
  - while we can poll sdl events:
    - create SDL2WindowEvent