Added ability to move onto next/previous tracks in Music Class
Music is now imported with a check for mp3/wav files only and will not need to be changed for new tracks added (unless it's a different file format)
Added variables for the future specifying song ranges for hubs/levels
You can now switch songs with N (next track) and B (previous track) in levels
WARNING: Letting you know that these resolves #413 and resolves #416 only to an extent. Currently, there are no specific songs specified for each level set or hub, which limits how this will be implemented now vs. later. Therefore, when we start to make more music with specific themes for these levels/hubs, it'll be easier to add it then (only a few lines in both kog_levels/kog_class) rather than make workarounds now and remove them later.
WARNING: Letting you know that these resolves #413 and resolves #416 only to an extent. Currently, there are no specific songs specified for each level set or hub, which limits how this will be implemented now vs. later. Therefore, when we start to make more music with specific themes for these levels/hubs, it'll be easier to add it then (only a few lines in both kog_levels/kog_class) rather than make workarounds now and remove them later.