`SDL2Game` now overrides `{initialize, finalize}` methods;
Added private `{initialize_sdl2, finalize_sdl2}` methods
Added declaration of `SDL2Game::initialize`, which:
  - calls private "initialize" function
  - calls base method;

Added declaration of `SDL2Game::finalize`, which:
  - calls private "finalize" function
  - calls base method
Added `SDL2Game::initalize_sdl2` definition, which:
  - inits all SDL2 modules
  - set hints "render_scale_quality" to "1";

Added `SDL2Game::finalize_sdl2` definition, which:
  - quits SDL2