Major refactoring - now using far more logical class names.

- Renamed "OsuFile" to "Beatmap".  All related variables and methods with "osu" have also been renamed to "beatmap" (or variants of each).
- Renamed "OsuGroupNode" to "BeatmapSetNode".  Avoids confusion since groups are identified by a "set ID", not a "group ID".
- Renamed "OsuGroupList" to "BeatmapSetList", for the same reason as above.
- Renamed "OsuDB" to "BeatmapDB", for the same reason as above.
- Moved classes directly related to parsed beatmaps (Beatmap, BeatmapSetList, BeatmapSetNode, OsuHitObject, and TimingPoint) into a new "beatmap" package.

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

src/itdelatrisu/opsu/downloads/DownloadNode.java

@@ -21,9 +21,9 @@ package itdelatrisu.opsu.downloads;
 import itdelatrisu.opsu.ErrorHandler;
 import itdelatrisu.opsu.GameImage;
 import itdelatrisu.opsu.Options;
-import itdelatrisu.opsu.OsuGroupList;
 import itdelatrisu.opsu.UI;
 import itdelatrisu.opsu.Utils;
+import itdelatrisu.opsu.beatmap.BeatmapSetList;
 import itdelatrisu.opsu.downloads.Download.DownloadListener;
 import itdelatrisu.opsu.downloads.Download.Status;
 import itdelatrisu.opsu.downloads.servers.DownloadServer;
@@ -325,7 +325,7 @@ public class DownloadNode {
 		g.fillRect(buttonBaseX, y, buttonWidth, buttonHeight);
 
 		// map is already loaded
-		if (OsuGroupList.get().containsBeatmapSetID(beatmapSetID)) {
+		if (BeatmapSetList.get().containsBeatmapSetID(beatmapSetID)) {
 			g.setColor(Utils.COLOR_BLUE_BUTTON);
 			g.fillRect(buttonBaseX, y, buttonWidth, buttonHeight);
 		}