refactored main
added VSYNC
introduced FrameUpdateListener interface
added mouse down handling to SDLEventDispatcher
StaticBoard should_display_nothing_when_created
StaticBoard should_display_added_items_according_to_board_position_and_grid_size
StaticBoard should_fail_when_added_item_has_invalid_id
Game should_notify_observer_about_filling_the_board_with_generated_items_when_game_is_started
added SDLSprite
extracted GameRunnerFactory from main
removed SampleTest
changed std::initializer_list to std::vector in StaticBoard ctor
removed creation from SDLGameUI, added SDLRendererFactory and gem images
connected StaticBoard with Game using GameObserver, fixed board coordinates