Fix problems from units branch merge conflicts

.clang-format

CMakeLists.txt

README.md

level-spezifikation.md

src/assets/ARCADECLASSIC.TTF

src/assets/main_background.png

src/building.cpp

src/building.hpp

src/effect.cpp

src/effect.hpp

src/engine.cpp

src/engine.hpp

src/level.cpp

src/level.hpp

src/main.cpp

src/scene.hpp

src/spritesheet.cpp

src/spritesheet.hpp

src/tile.cpp

src/tile.hpp