Modified file structure and working player animations
- Moved menus and corresponding scripts into Menus folder
- Renamed art folder into Assets folder
- Made Levels folder and moved test_level there
- Moved player scripts and scene into Player folder
- Player has state machine for handling player state (ground, air, landing and attack)
- Made working player animations for (idle, run, jump, double jump, land, attack 1, attack 2)