Main acting as a swithc

Main acts as a switch between InGameState and InMainMenuState, enabling
and disabling them one at a time.
Connecting gameOver and restartLevel with Main

Crashes on player death!
setEnabled(false) pauses game

inGameState.setEnabled(false) now pauses player and enemy movement.
Does not pause particle movements.
Gameover brings up menu

Game-over menu still same as start menu, seen on top of player hanging
in mid-air.
Merge branch 'menu-dev'