I've updated property class which is now a bit smaller but also more lightweight and easy to maintain for me. Also rewritten entity serializer/deserializer, even made it to save physics body's velocities (may be useful for saving game?). Also got rid of command system since it worked pretty slow. I think everything will communicate based on events and I might also make some sort of linking system so I could do the same chaining effect without too much overhead, only on load of the level :)
Also wrote an InputReceiver which supports four key states (UP/PRESSED/DOWN/RELEASED), also supports double tapping in a defined interval of time (eg. 100ms).