Single Player Menu

[mrub]

• Make all levels appear and come up with visual representation of locked/unlocked levels
• Clicking on single player takes you either to the last level you beat, or to the 2nd page (possibly just array index 1, or to the last page

[gregmclain]

Changed menu to display level preview if the level is unlocked, and display a lock sprite if the level is not unlocked. We just have to create a new lock sprite to display. The menu is designed to display the page containing the last level that the user completed.