Crap player

1. Controller and keyboard detection
   • Player input comes from signal(s). Used by menus and vehicle.
2. Player count detection (up to 4 players)
   • Player count is sent by signals. Main menu can then display player count and in the game we can have splitscreen appear based on the player count.
3. Ground detection
   • If all wheels of a car send a signal for being in contact with the ground, the double jump gets reset. The signal is used to reset the jump state and UI jump indicator.