Fixed level packs and music with intros

I've fixed some bugs. Here they are:

• Level Packs. Previously, loading a level pack would cause the game to load the levels into the level select, but then, rather than displaying the level select, it would show the level you had in the editor, but in puzzle mode. Now it automatically shows the level select when a level pack is loaded.
• Music with intros. Before this fix, music with intros (track 4 and 5) wouldn't switch to the main loop if you were in the level select when they should switch. Now they switch whether you are in the level select or not.