Prevent saving during the tutorial

[BenjaminAmos]

Description

This pull request attempts to fix areas where the game still saves whilst the tutorial is active. This is only a temporary solution and changes to SaveManager may provide a more comprehensive one in the future.

Testing

• Start a new game
• Buy an item
• Exit to the main menu
• Start the tutorial
• Exit the tutorial
• Continue your last game
• The item you bought previously, along with your last save data, should be present

This should fix #699.