Minor updates.

- Draw the playfield background in the song menu if a background cannot be drawn for the focused beatmap.
- Added ScoreDB.deleteScore() method to delete a score from the database.
- Added @author tags for curve-related classes (by fluddokt, #12).

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

src/itdelatrisu/opsu/objects/curves/LinearBezier.java

@@ -31,6 +31,8 @@ import org.newdawn.slick.Image;
 /**
  * Representation of a Bezier curve with equidistant points.
  * http://pomax.github.io/bezierinfo/#tracing
+ *
+ * @author fluddokt (https://github.com/fluddokt)
  */
 public class LinearBezier extends Curve {
 	/** The angles of the first and last control points for drawing. */