Resolved some reported issues.

- Threaded OGG loading (in addition to MP3) to eliminate delays in song select menu. (reported by xasuma)
- Changed default OSZ unpacking location to a "SongPacks" directory to prevent unintended unpacking. (reported by Lanturn)
- Fixed a null pointer for a corner case in 'getRandomNode()'. (reported by @iceblade112)

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

.gitignore

@@ -1,6 +1,7 @@
 /.opsu_tmp/
 /Screenshots/
 /Skins/
+/SongPacks/
 /Songs/
 /.opsu.log
 /.opsu.cfg