FEATURE: Main Menu

[mroobit]

Implement a menu screen (for game mode Menu) after load screen, with following selections

• New Game
• Load Save File
• How To Play/Controls
• Settings
• Credits/Acknowledgements
• Exit

Prerequisites

• [x] Implement Save Files #7
• [ ] Create How-To
• [ ] Create Settings
• [ ] Create Credits
• [ ] optional: Find New Font

[mroobit]

Implemented menu (doubly-linked list with basic display using tinne26's etxt). Currently only "New Game" and "Exit" do anything. (Relevant Commit)