V013.01

- Implemented pause screen (almost finished) and SaveGameScreen (still
empty).  Changed SPC key to do enter, to RETURN key.
- Deleted useless bool on GamePlayScreen.
- If you press P during the game, then you go to PauseScreen
- Fixed bug that caused that screens never got close. They close now.
- Deleted useless option on OptionsScreen that let you to IntroScreen.
(not  needed now because the fix of the bug).