Added NoteColorMode ProgressOnBeatAtEnd

Almost the same as progress, but 4ths use the last frame rather than the first.
This lets rainbow and vivid from DDR be made properly.

src/NoteDisplay.h

@@ -36,6 +36,7 @@ enum NoteColorType
 {
 	NoteColorType_Denominator, /**< Color by note type. */
 	NoteColorType_Progress, /**< Color by progress. */
+	NoteColorType_ProgressOnBeatAtEnd, /**< Color by progress, except 4th notes are considered to occur at the end of the beat. */
 	NUM_NoteColorType,
 	NoteColorType_Invalid
 };