Remove all usage of `BaseDifficulty` (and access `Difficulty` instead)
AuthorString
BaseDifficulty
Difficulty
TestScenePresentScore
BeatmapSetInfo.Metadata
.Result
.WaitSafelyForResult
OnlineID
Initialise `BeatmapSet.Beatmaps` list at construction time
Beatmap
BeatmapSetInfo
BeatmapSetInfo.OnlineBeatmapSetID
BeatmapInfo.OnlineBeatmapID
Add `ILive<T>` and use as return type of `Import` methods
BeatmapInfo Beatmap
ILive