Prevent downloading songs that are already loaded. (base: fluddokt/opsu/76778f8)

- All beatmap set IDs are now stored in a set in OsuGroupList.
- OsuParser now checks the directory name for beatmap set IDs if the OsuFile doesn't contain one (for older beatmap formats).

Tweaks:
- Clear completed downloads when hitting "Import All".
- Call Download.updateReadSoFar() upon starting downloads instead of waiting for user to hover over the button (causing an unnecessary delay).

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

src/itdelatrisu/opsu/Options.java

@@ -392,8 +392,8 @@ public class Options {
 		RES_1366_768 (1366, 768),
 		RES_1440_900 (1440, 900),
 		RES_1600_900 (1600, 900),
-		RES_1680_1050 (1680, 1050),
 		RES_1600_1200 (1600, 1200),
+		RES_1680_1050 (1680, 1050),
 		RES_1920_1080 (1920, 1080),
 		RES_1920_1200 (1920, 1200),
 		RES_2560_1440 (2560, 1440),