Merge branch 'compatibility'
Add utils
Add State_manager
Add Base_state
Add Splash_state
Add main.cpp
Add gamelogic utilities
Add gamelogic::Entity interface
Add states::Ingame_state
Add gamelogic::Actor base class
Add content::Packman
Add gamelogic::Tile base class
Add content::Wall
Add gamelogic::Level
Add example level
Use ingame state as splash.post
Update README.md