using
# Conflicts: # osu.Game/Beatmaps/Beatmap.cs
Also ensures some extra fields inside Beatmap have non-null defaults.
Also fixes circular references when using IJsonSerializable.
# Conflicts: # osu.Game.Rulesets.Mania/UI/Column.cs
Add legacy beatmap flag.
Moves star difficulty calculation entry-point to Beatmap, and sets star difficulty at the correct place for song select to display.